Work on Mac GN build

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 8613d1fe584b61e6d68e131da7c7f0558c47cf02..c9a58b4ba0296565c3b79bd34b0134cee4fe012e 100644
--- a/build/toolchain/mac/BUILD.gn
+++ b/build/toolchain/mac/BUILD.gn
@@ -19,30 +19,6 @@ if (is_clang) {
                    root_build_dir)
   cxx = rebase_path("//third_party/llvm-build/Release+Asserts/bin/clang++",
                     root_build_dir)
-
-  # Set the GYP header for all toolchains when running under Clang.
-  if (is_gyp) {
-    make_global_settings = make_clang_global_settings
-
-    if (use_goma) {
-      # There is a TODO(yyanagisawa) in common.gypi about the make generator not
-      # supporting CC_wrapper without CC. As a result, we must add a condition
-      # when on the generator when we're not explicitly setting the variables
-      # above (which happens when gyp_header is empty at this point).
-      #
-      # GYP will interpret the file once for each generator, so we have to write
-      # this condition into the GYP file since the user could have more than one
-      # generator set.
-      gyp_header =
-        "'conditions':" +
-        "[['\"<(GENERATOR)\"==\"ninja\"', { 'make_global_settings': [" +
-        make_global_settings +
-        make_goma_global_settings +
-        "]}]],"
-    } else {
-      gyp_header = "'make_global_settings': [" + make_global_settings + "],"
-    }
-  }
 } else {
   cc = "gcc"
   cxx = "g++"