use icf=safe w/ gcc+gold+x86/x64, icf=all w/ gold elsewhere.

This is another attempt to fix which flags we use by default when
linking w/ gold. The interaction of gold + gcc on intel platforms
appears buggy, so we only use icf=safe there; gold + gcc on non-intel
platforms, and gold + clang on intel can use icf=all, as long
as we have the latest binutils.

This change is GN-only, since linux GYP builds are on their last
breaths and it's not worth worrying about x86 flags there.

R=mcgrathr@chromium.org, thakis@chromium.org
BUG=576197

Review-Url: https://codereview.chromium.org/1952353004
Cr-Original-Commit-Position: refs/heads/master@{#393563}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a403dd9d7c3b7d3619da3ef989f4666e1e11cf95

config/compiler/BUILD.gn

@@ -350,7 +350,13 @@ config("compiler") {
 
   if (is_posix && (use_gold || (use_lld && !is_nacl)) && !using_sanitizer &&
       !(is_android && use_order_profiling)) {
-    ldflags += [ "-Wl,--icf=all" ]
+    # TODO(crbug.com/576197) - gcc on x86 platforms + gold + icf=all
+    # doesn't currently work. Once it does, use icf=all everywhere.
+    if (is_clang || (target_cpu != "x86" && target_cpu != "x64")) {
+      ldflags += [ "-Wl,--icf=all" ]
+    } else {
+      ldflags += [ "-Wl,--icf=safe" ]
+    }
   }
 
   if (linux_use_bundled_binutils) {