[Mac/GN] Do not use ELF-only cflags on Mac.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index f9e01af1968300094eb290adc62c0786902d420d..75779d4c19d011d5f478b9e06c87aea8e8d531a1 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1226,16 +1226,7 @@ if (is_win) {
     }
   }
 } else {
-  common_optimize_on_cflags = [
-    # Don't emit the GCC version ident directives, they just end up in the
-    # .comment section taking up binary size.
-    "-fno-ident",
-
-    # Put data and code in their own sections, so that unused symbols
-    # can be removed at link time with --gc-sections.
-    "-fdata-sections",
-    "-ffunction-sections",
-  ]
+  common_optimize_on_cflags = []
   common_optimize_on_ldflags = []
 
   if (is_android) {
@@ -1262,7 +1253,19 @@ if (is_win) {
       common_optimize_on_ldflags += [ "-Wl,-dead_strip" ]
     }
   } else {
-    # Non-Mac Posix linker flags.
+    # Non-Mac Posix flags.
+
+    common_optimize_on_cflags += [
+      # Don't emit the GCC version ident directives, they just end up in the
+      # .comment section taking up binary size.
+      "-fno-ident",
+
+      # Put data and code in their own sections, so that unused symbols
+      # can be removed at link time with --gc-sections.
+      "-fdata-sections",
+      "-ffunction-sections",
+    ]
+
     common_optimize_on_ldflags += [
       # Specifically tell the linker to perform optimizations.
       # See http://lwn.net/Articles/192624/ .