mac: Don't run dump_syms or produce a .dSYM archive in component builds

dump_syms and the .dSYM archiver are intended for use on official
Chrome-branded builds. While they work in other configurations, they
draw from a static list of data sources that match what ships in an
official build. Component builds break code out into many other modules,
none of which are in the static list. Any output produced by the
chrome_dump_syms or chrome_dsym_archive targets would be misleadingly
unusable in a component build.

To avoid producing these pointless artifacts, disable their function
(while leaving the target names viable via empty "group" definitions, in
case anyone depends on them.)

Note that the chrome target never depends on either of these targets in
a component build. These targets are only reachable explicitly or via a
full build.

Bug: 991206
Change-Id: I8b6e09f78896da1e02f8dabd2d60d0fd42df2ef4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1742213Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685358}

chrome/BUILD.gn

@@ -1374,7 +1374,13 @@ if (is_win) {
     }
   }
 
-  if (enable_dsyms) {
+  if (enable_dsyms && !is_component_build) {
+    # It is possible to run dump_syms on unstripped products without dSYMs, but
+    # doing so isn't logical and won't happen in practice. It's also pointless
+    # to run dump_syms or archive dSYMs in a component build, where all of the
+    # interesting symbols and debug info are tucked away in other libraries
+    # beyond the set explicitly listed here.
+
     # This list must be updated with the two targets' deps list below, and
     # the list of _dsyms in :chrome_dsym_archive.
     _chrome_symbols_sources = [
@@ -1390,8 +1396,6 @@ if (is_win) {
       _chrome_symbols_sources += [ "$root_out_dir/${chrome_helper_name}${helper_params[2]}.app/Contents/MacOS/${chrome_helper_name}${helper_params[2]}" ]
     }
 
-    # It is possible to run dump_syms on unstripped products without dSYMs,
-    # but doing so isn't logical and won't happen in practice.
     action_foreach("chrome_dump_syms") {
       script = "//build/redirect_stdout.py"
 
@@ -1939,11 +1943,11 @@ if (is_linux) {
   if (is_official_build) {
     group("linux_symbols") {
       deps = [
+        ":angle_egl_symbols",
+        ":angle_gles_symbols",
         ":chrome_symbols",
         ":swiftshader_egl_symbols",
         ":swiftshader_gles_symbols",
-        ":angle_egl_symbols",
-        ":angle_gles_symbols",
       ]
     }
     extract_symbols("chrome_symbols") {