mac/asan: Enable asan use-after-scope checking.

-fsanitize-address-use-after-scopes is on by default, so stop explicitly
passing it on non-mac. This is a no-op.

Stop passing -fno-sanitize-address-use-after-scope on mac, to enable
the feature there too.

Bug: 708216,708707
Cq-Include-Trybots: luci.chromium.try:mac_chromium_asan_rel_ng
Change-Id: I406ec8c80997291f7467b51c4f50d573ea90052f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2526804
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827634}

build/config/sanitizers/BUILD.gn

@@ -157,12 +157,6 @@ config("default_sanitizer_ldflags") {
     ldflags = []
     if (is_asan) {
       ldflags += [ "-fsanitize=address" ]
-      if (is_mac) {
-        # https://crbug.com/708707
-        ldflags += [ "-fno-sanitize-address-use-after-scope" ]
-      } else {
-        ldflags += [ "-fsanitize-address-use-after-scope" ]
-      }
     }
     if (is_hwasan) {
       ldflags += [ "-fsanitize=hwaddress" ]
@@ -277,12 +271,6 @@ config("asan_flags") {
   cflags = []
   if (is_asan) {
     cflags += [ "-fsanitize=address" ]
-    if (!is_mac) {
-      cflags += [ "-fsanitize-address-use-after-scope" ]
-    } else {
-      # https://crbug.com/708707
-      cflags += [ "-fno-sanitize-address-use-after-scope" ]
-    }
     if (asan_use_blacklist) {
       if (is_win) {
         if (!defined(asan_win_blacklist_path)) {