Revert "[ios] Always use symbolic links to system Xcode in build_root_dir"

This reverts commit a06a6eb7.

Reason for revert: Seems to break non-goma builds on macos.

Original change's description:
> [ios] Always use symbolic links to system Xcode in build_root_dir
>
> Goma RBE only supports paths that are relative to the source dir
> while build not using Goma or using old Goma backend supports both
> so always use symbolic link to system Xcode on iOS.
>
> This fix the compilation for people using Goma as Goma RBE is now
> the default backend and without this change, the build would fall
> back to local compilation, drastically slowing the build.
>
> Stop using the ios_enable_relative_sdk_path and ios_use_goma_rbe
> gn variables as they are now always expected to be `true`. Keep
> the variable ios_use_goma_rbe to avoid breaking the bots that do
> override the value but ignore it (bot set it to true anyway).
>
> Bug: none
> Change-Id: I2a3c098304594fb20491ab92100e9a4101a048db
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2555117
> Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#830616}

TBR=thakis@chromium.org,sdefresne@chromium.org

Change-Id: I5aed7d701a1d2d04d389cb4d746bc975e80b0f0f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: none
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2561019Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831019}

build/config/compiler/compiler.gni

@@ -19,7 +19,7 @@ if (current_cpu == "arm" || current_cpu == "arm64") {
   import("//build/config/arm.gni")
 }
 
-if (is_apple) {
+if (is_mac) {
   import("//build/config/mac/symbols.gni")
 }
 
@@ -216,7 +216,7 @@ declare_args() {
 # official builders.
 strip_absolute_paths_from_debug_symbols_default =
     is_android || is_fuchsia || is_nacl || (is_win && use_lld) || is_linux ||
-    is_chromeos || (is_apple && !enable_dsyms)
+    is_chromeos || (is_mac && !enable_dsyms) || ios_use_goma_rbe
 
 # If the platform uses stripped absolute paths by default, then we don't expose
 # it as a configuration option. If this is causing problems, please file a bug.

build/config/ios/BUILD.gn

@@ -87,11 +87,14 @@ config("compiler") {
 # that is iOS-only. Please see that target for advice on what should go in
 # :runtime_library vs. :compiler.
 config("runtime_library") {
-  # The variable ios_sdk_path is relative to root_out_dir for goma RBE. As it
-  # is passed to the compiler via cflags, ldflags which do not rebase the
-  # values (since they are compiler flags, not paths), it has to rebased. Use
-  # a local variable to avoid repeating the rebase invocation.
-  _sdk_root = rebase_path(ios_sdk_path, root_build_dir)
+  # The variable ios_sdk_path may be relative to root_out_dir on the bots. As
+  # it is passed to the compiler via cflags, ldflags which do not rebase the
+  # values (since they are compiler flags, not paths), it may be required to
+  # rebase it. Use a local variable to avoid repeating the rebase invocation.
+  _sdk_root = ios_sdk_path
+  if (ios_enable_relative_sdk_path) {
+    _sdk_root = rebase_path(ios_sdk_path, root_build_dir)
+  }
 
   common_flags = [
     "-isysroot",
@@ -219,14 +222,16 @@ _xctrunner_path =
 #
 # To workaround this, add a target that pretends to create those files
 # (but does nothing). See https://crbug.com/1061487 for why this is needed.
-action("copy_xctrunner_app") {
-  testonly = true
-  script = "//build/noop.py"
-  outputs = [
-    "$_xctrunner_path/Info.plist",
-    "$_xctrunner_path/PkgInfo",
-    "$_xctrunner_path/XCTRunner",
-  ]
+if (ios_use_goma_rbe) {
+  action("copy_xctrunner_app") {
+    testonly = true
+    script = "//build/noop.py"
+    outputs = [
+      "$_xctrunner_path/Info.plist",
+      "$_xctrunner_path/PkgInfo",
+      "$_xctrunner_path/XCTRunner",
+    ]
+  }
 }
 
 # When creating the test runner for an XCUITest, the arm64e slice of the binary
@@ -246,5 +251,7 @@ action("xctest_runner_without_arm64e") {
     xcode_version,
   ]
 
-  deps = [ ":copy_xctrunner_app" ]
+  if (ios_use_goma_rbe) {
+    deps = [ ":copy_xctrunner_app" ]
+  }
 }

build/config/ios/ios_sdk.gni

@@ -58,6 +58,9 @@ declare_args() {
   # You can also pass the value via "--args" parameter for "gn gen" command by
   # using the syntax --args='additional_target_cpus=["arm"] target_cpu="arm64"'.
   additional_target_cpus = []
+
+  # TODO(crbug.com/1015730): remove this flag because ios_use_goma_rbe covers.
+  ios_enable_relative_sdk_path = ios_use_goma_rbe
 }
 
 declare_args() {
@@ -127,8 +130,6 @@ if (ios_sdk_path == "") {
   ios_sdk_info_args = [
     "--get_sdk_info",
     "--get_machine_info",
-    "--create_symlink_at",
-    "sdk/xcode_links",
   ]
   ios_sdk_info_args += [ ios_sdk_name ]
   if (ios_sdk_developer_dir != "") {
@@ -137,6 +138,12 @@ if (ios_sdk_path == "") {
       ios_sdk_developer_dir,
     ]
   }
+  if (ios_use_goma_rbe) {
+    ios_sdk_info_args += [
+      "--create_symlink_at",
+      "sdk/xcode_links",
+    ]
+  }
   script_name = "//build/config/mac/sdk_info.py"
   _ios_sdk_result = exec_script(script_name, ios_sdk_info_args, "scope")
   ios_sdk_path = _ios_sdk_result.sdk_path

build/config/ios/rules.gni

@@ -433,8 +433,15 @@ template("create_signed_bundle") {
       code_signing_args += [ "--disable-code-signature" ]
     }
     if (defined(invoker.extra_system_frameworks)) {
+      # All framework in extra_system_frameworks are expected to be system
+      # framework and the path to be already system absolute so do not use
+      # rebase_path here unless ios_enable_relative_sdk_path is trued.
       foreach(_framework, invoker.extra_system_frameworks) {
-        _framework_path = rebase_path(_framework, root_build_dir)
+        if (ios_enable_relative_sdk_path) {
+          _framework_path = rebase_path(_framework, root_build_dir)
+        } else {
+          _framework_path = _framework
+        }
         code_signing_args += [ "-F=$_framework_path" ]
       }
     }
@@ -1967,7 +1974,9 @@ template("ios_xcuitest_test_runner_bundle") {
              "-o=" + rebase_path(_output_name, root_build_dir),
            ] + rebase_path(sources, root_build_dir)
 
-    deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    if (ios_use_goma_rbe) {
+      deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    }
   }
 
   ios_info_plist(_info_plist_target) {
@@ -1997,7 +2006,9 @@ template("ios_xcuitest_test_runner_bundle") {
 
     outputs = [ "{{bundle_contents_dir}}/PkgInfo" ]
 
-    public_deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    if (ios_use_goma_rbe) {
+      public_deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    }
   }
 
   _xctest_bundle = invoker.xctest_bundle

build/config/mac/mac_sdk.gni

@@ -77,7 +77,7 @@ if (!use_system_xcode) {
 }
 
 # put system xcode under src to avoid absolute path.
-if (use_system_xcode) {
+if (use_system_xcode && ios_use_goma_rbe) {
   sdk_info_args += [
     "--get_sdk_info",
     "--create_symlink_at",
@@ -89,7 +89,7 @@ sdk_info_args += [ mac_sdk_name ]
 _mac_sdk_result = exec_script(script_name, sdk_info_args, "scope")
 xcode_version = _mac_sdk_result.xcode_version
 xcode_build = _mac_sdk_result.xcode_build
-if (mac_sdk_path == "" && use_system_xcode) {
+if (mac_sdk_path == "" && use_system_xcode && ios_use_goma_rbe) {
   mac_sdk_path = _mac_sdk_result.sdk_path
 }
 

build/toolchain/goma.gni

@@ -25,9 +25,8 @@ declare_args() {
   # TODO(crbug.com/726475): true if use_goma = true in the future.
   use_java_goma = false
 
-  # Deprecated and ignored as Goma RBE is now the default. Still exists
-  # to avoid breaking the build on the bots. Will be removed when all
-  # bots have been configured to not set this variable.
+  # Auto-configure for Goma RBE backend.
+  # TODO(crbug.com/1015730): true if use_goma = true in the future.
   ios_use_goma_rbe = false
 }
 

docs/ios/build_instructions.md

@@ -328,23 +328,6 @@ ask there. As mentioned above, be sure that the
 [waterfall](https://build.chromium.org/buildbot/waterfall/) is green and the tree
 is open before checking out. This will increase your chances of success.
 
-### Debugging
-
-To help with reproductible builds, and to work with Goma, the path to source
-files in debugging symbols are relative to source directory. To allow Xcode
-to find the source files, you need to ensure to have an `~/.lldbinit-Xcode`
-file with the following lines into it (substitute {SRC} for your actual path
-to the root of Chromium's sources):
-
-```
-script sys.path[:0] = ['{SRC}/tools/lldb']
-script import lldbinit
-```
-
-This will also allow you to see the content of some of Chromium types in the
-debugger like `base::string16`, ... If you want to use `lldb` directly, name
-the file `~/.lldbinit` instead of `~/.lldbinit-Xcode`.
-
 ### Changing the version of Xcode
 
 To change the version of Xcode used to build Chromium on iOS, please follow