[Mac/GN] Implement dSYM generation and stripping.

build/toolchain/mac/BUILD.gn

Index: build/toolchain/mac/BUILD.gn
diff --git a/build/toolchain/mac/BUILD.gn b/build/toolchain/mac/BUILD.gn
index 82eacab28eba0fb0596b1ec649ae3dc20ee422c0..9a597f42d635f9fbd08ab9e4b42e57357d1301ed 100644
--- a/build/toolchain/mac/BUILD.gn
+++ b/build/toolchain/mac/BUILD.gn
@@ -138,7 +138,10 @@ template("mac_toolchain") {
 
       does_reexport_command = "[ ! -e \"$dylib\" -o ! -e \"$tocname\" ] || otool -l \"$dylib\" | grep -q LC_REEXPORT_DYLIB"
 
-      link_command = "$ld -shared "
+      linker_driver =
+          rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)

[Dirk Pranke, 2016/05/20 01:47:19]

You should be able to hoist this up into a file-scoped variable, rather than
having to repeat it three times.

[Robert Sesek, 2016/05/20 15:15:36]

I tried doing it at the file-level but GN complained it was unused. Moved it up
into the toolchain, though.

[Dirk Pranke, 2016/05/20 16:43:55]

Oh, yeah, usage doesn't propagate across templates. Well, into the template is
good enough.

+
+      link_command = "$linker_driver $ld -shared "
       if (is_component_build) {
         link_command += " -Wl,-install_name,@rpath/\"{{target_output_name}}{{output_extension}}\" "
       }
@@ -180,8 +183,10 @@ template("mac_toolchain") {
       sofile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"  # eg "./libfoo.so"
       rspfile = sofile + ".rsp"
 
-      link_command =
-          "$ld -bundle {{ldflags}} -o \"$sofile\" -Wl,-filelist,\"$rspfile\""
+      linker_driver =
+          rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)
+
+      link_command = "$linker_driver $ld -bundle {{ldflags}} -o \"$sofile\" -Wl,-filelist,\"$rspfile\""
       if (is_component_build) {
         link_command += " -Wl,-install_name,@rpath/{{target_output_name}}{{output_extension}}"
       }
@@ -215,7 +220,10 @@ template("mac_toolchain") {
       # do for command-line arguments. Thus any source names with spaces, or
       # label names with spaces (which GN bases the output paths on) will be
       # corrupted by this process. Don't use spaces for source files or labels.
-      command = "$ld {{ldflags}} -o \"$outfile\" -Wl,-filelist,\"$rspfile\" {{solibs}} {{libs}}"
+      linker_driver =
+          rebase_path("//build/toolchain/mac/linker_driver.py", root_build_dir)
+
+      command = "$linker_driver $ld {{ldflags}} -o \"$outfile\" -Wl,-filelist,\"$rspfile\" {{solibs}} {{libs}}"
       description = "LINK $outfile"
       rspfile_content = "{{inputs_newline}}"
       outputs = [