gn: Add chromium_builder_asan target.

All the LKGR clusterfuzz bots build this target, so add it to allow
switching these bots to gn.

BUG=618702,542853,619086
TBR=eroman

Review-Url: https://codereview.chromium.org/2059843002
Cr-Original-Commit-Position: refs/heads/master@{#399241}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3f7d4fc75b62ca7008642c5aea6233eade695da5

all.gyp

@@ -708,6 +708,7 @@
                 '../third_party/pdfium/samples/samples.gyp:pdfium_test',
               ],
             }],
+            # TODO(thakis): Remove this block, nothing ever sets this.
             ['internal_filter_fuzzer==1', {
               'dependencies': [
                 '../skia/tools/clusterfuzz-data/fuzzers/filter_fuzzer/filter_fuzzer.gyp:filter_fuzzer',

sanitizers/BUILD.gn

@@ -2,8 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-if (is_linux && !is_chromeos) {
-  # TODO(GYP): Figure out which of these work and are needed on other platforms.
+if (is_clang) {
   copy("copy_llvm_symbolizer") {
     if (is_win) {
       sources = [

sanitizers/sanitizers.gyp

@@ -66,6 +66,7 @@
         ],
       },
     },
+    # GN version: //build/sanitizers:copy_llvm_symbolizer
     {
       # Copy llvm-symbolizer to the product dir so that LKGR bots can package it.
       'target_name': 'llvm-symbolizer',