[libFuzzer][AFL] Enable fuzzer builds with SanitizerCoverage and without A/M/UbSan.

build/config/sanitizers/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 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")
 
@@ skipping 148 matching lines @@
     if (is_ubsan || is_ubsan_security) {
       ldflags += [ "-fsanitize=undefined" ]
     }
     if (is_ubsan_null) {
       ldflags += [ "-fsanitize=null" ]
     }
     if (is_ubsan_vptr) {
       ldflags += [ "-fsanitize=vptr" ]
     }
 
+    if (use_sanitizer_coverage) {
+      ldflags += [ "-fsanitize-coverage=$sanitizer_coverage_flags" ]
+    }
+
     if (is_cfi && !is_nacl) {
       ldflags += [ "-fsanitize=cfi-vcall" ]
       if (use_cfi_cast) {
         ldflags += [
           "-fsanitize=cfi-derived-cast",
           "-fsanitize=cfi-unrelated-cast",
         ]
       }
       if (use_cfi_diag) {
         ldflags += [
@@ skipping 278 matching lines @@
 # This allows to selectively disable ubsan_vptr, when needed. In particular,
 # if some third_party code is required to be compiled without rtti, which
 # is a requirement for ubsan_vptr.
 config("default_sanitizer_flags_but_ubsan_vptr") {
   configs = all_sanitizer_configs - [ ":ubsan_vptr_flags" ]
 }
 
 config("default_sanitizer_flags_but_coverage") {
   configs = all_sanitizer_configs - [ ":coverage_flags" ]
 }