[sanitizers] asan_globals GN option

Detect overflow/underflow for global objects.
Enabled by default with asan, except for Android & Mac.

Review-Url: https://codereview.chromium.org/2130893002
Cr-Commit-Position: refs/heads/master@{#404918}

build/config/sanitizers/BUILD.gn

@@ -206,6 +206,12 @@ config("asan_flags") {
   cflags = []
   if (is_asan) {
     cflags += [ "-fsanitize=address" ]
+    if (!asan_globals) {
+      cflags += [
+        "-mllvm",
+        "-asan-globals=0",
+      ]
+    }
     if (is_win) {
       cflags += [ "-fsanitize-blacklist=" +
                   rebase_path("//tools/memory/asan/blacklist_win.txt",
@@ -216,23 +222,8 @@ config("asan_flags") {
           [ "-fsanitize-blacklist=" +
             rebase_path("//tools/memory/asan/blacklist.txt", root_build_dir) ]
     }
-    if (is_android) {
-      # Android build relies on -Wl,--gc-sections removing unreachable code.
-      # ASan instrumentation for globals inhibits this and results in a
-      # library with unresolvable relocations.
-      # TODO(eugenis): find a way to reenable this.
-      cflags += [
-        "-mllvm",
-        "-asan-globals=0",
-      ]
-    } else if (is_mac) {
-      # http://crbug.com/352073
-      cflags += [
-        "-mllvm",
-        "-asan-globals=0",
-      ]
-      # TODO(GYP): deal with mac_bundles.
-    } else if (is_win) {
+
+    if (is_win) {
       assert(current_cpu == "x86", "WinASan is 32-bit only currently")
       if (is_component_build) {
         libs = [

build/config/sanitizers/sanitizers.gni

@@ -78,7 +78,6 @@ declare_args() {
   # trace-pc
   # Default value when unset and use_sanitizer_coverage=true:
   #     edge,indirect-calls,8bit-counters
-
   sanitizer_coverage_flags = ""
 }
 
@@ -96,6 +95,16 @@ declare_args() {
   # Enable -fsanitize-coverage.
   use_sanitizer_coverage =
       use_libfuzzer || use_afl || sanitizer_coverage_flags != ""
+
+  # Detect overflow/underflow for global objects.
+  #
+  # Android build relies on -Wl,--gc-sections removing unreachable code.
+  # ASan instrumentation for globals inhibits this and results in a
+  # library with unresolvable relocations.
+  # TODO(eugenis): find a way to reenable this.
+  #
+  # Mac: http://crbug.com/352073
+  asan_globals = !is_android && !is_mac
 }
 
 if (use_afl && sanitizer_coverage_flags == "") {