Disable "pc-table" instrumentation for libFuzzer builds on Mac.

Bug: 926588
Change-Id: Id336e9fa0db4f01eacee252a5cd17e9d967159ed
Reviewed-on: https://chromium-review.googlesource.com/c/1447016Reviewed-by: Jonathan Metzman <metzman@chromium.org>
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627949}

build/config/sanitizers/BUILD.gn

@@ -2,12 +2,12 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build_overrides/build.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/clang/clang.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
+import("//build_overrides/build.gni")
 
 if (is_ios) {
   import("//build/config/ios/ios_sdk.gni")
@@ -201,6 +201,11 @@ config("default_sanitizer_ldflags") {
     if (use_sanitizer_coverage) {
       if (use_libfuzzer) {
         ldflags += [ "-fsanitize=fuzzer-no-link" ]
+        if (is_mac) {
+          # TODO(crbug.com/926588): on macOS, dead code stripping does not work
+          # well with `pc-table` instrumentation enabled by `fuzzer-no-link`.
+          ldflags += [ "-fno-sanitize-coverage=pc-table" ]
+        }
       } else {
         ldflags += [ "-fsanitize-coverage=$sanitizer_coverage_flags" ]
       }
@@ -399,6 +404,11 @@ config("coverage_flags") {
 
     if (use_libfuzzer) {
       cflags += [ "-fsanitize=fuzzer-no-link" ]
+      if (is_mac) {
+        # TODO(crbug.com/926588): on macOS, dead code stripping does not work
+        # well with `pc-table` instrumentation enabled by `fuzzer-no-link`.
+        cflags += [ "-fno-sanitize-coverage=pc-table" ]
+      }
     } else {
       cflags += [
         "-fsanitize-coverage=$sanitizer_coverage_flags",