Add missing linker flags to allow use of custom frameworks on iOS.

Pass required flags "-rpath @executable/Frameworks" when linking
executable to point to the location where the custom frameworks
are located in iOS builds.

Pass flags "-objc_abi_version 2" to linker flag for execuable and
dynamic libraries as is done by Xcode and remove one intermediate
config object (unnecessary).

BUG=None

Review-Url: https://codereview.chromium.org/2326543003
Cr-Commit-Position: refs/heads/master@{#417403}

build/config/ios/rules.gni

@@ -439,6 +439,20 @@ template("ios_app_bundle") {
     }
     libs += [ "UIKit.framework" ]
 
+    if (!defined(ldflags)) {
+      ldflags = []
+    }
+    ldflags += [
+      "-Xlinker",
+      "-rpath",
+      "-Xlinker",
+      "@executable_path/Frameworks",
+      "-Xlinker",
+      "-objc_abi_version",
+      "-Xlinker",
+      "2",
+    ]
+
     if (use_ios_simulator) {
       deps += [ ":$_generate_entitlements_target($default_toolchain)" ]
 
@@ -865,7 +879,6 @@ template("ios_framework_bundle") {
     _framework_headers_target = _target_name + "_framework_headers"
     _framework_headers_config = _target_name + "_framework_headers_config"
     _headers_map_config = _target_name + "_headers_map"
-    _install_name_config = _target_name + "_install_name"
   }
 
   _arch_shared_library_source = _target_name + "_arch_shared_library_sources"
@@ -925,7 +938,20 @@ template("ios_framework_bundle") {
       deps = []
     }
     deps += [ ":$_arch_shared_library_source" ]
-    configs += [ ":$_install_name_config($default_toolchain)" ]
+
+    if (!defined(ldflags)) {
+      ldflags = []
+    }
+    ldflags += [
+      "-Xlinker",
+      "-install_name",
+      "-Xlinker",
+      "@rpath/$_output_name.framework/$_output_name",
+      "-Xlinker",
+      "-objc_abi_version",
+      "-Xlinker",
+      "2",
+    ]
 
     output_extension = ""
     output_name = _output_name
@@ -1022,14 +1048,6 @@ template("ios_framework_bundle") {
         include_dirs = [ _header_map_filename ]
       }
 
-      config(_install_name_config) {
-        visibility = [ ":$_target_name" ]
-        ldflags = [
-          "-install_name",
-          "@rpath/$_output_name.framework/$_output_name",
-        ]
-      }
-
       group(_framework_headers_target) {
         deps = [
           ":$_compile_headers_map_target",