Enabled init_stack_vars for more non-official builds

This just enables the same flag as crrev.com/c/1795632

The following are still disabled:
Windows: blocked by llvm roll, which will make clang-cl recognize
-ftrivial-auto-var-init.
Android: android-kitkat-arm-rel consistently fails a test.
Clang shipped with XCode can be too old to support this flag.

Bug: 977230
Change-Id: I622ba8fea93ed65cf8cb01fab26df0fb5f26f12b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1838383Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711096}

build/config/compiler/BUILD.gn

@@ -138,11 +138,16 @@ declare_args() {
   # By default only the binaries in official builds get build IDs.
   force_local_build_id = false
 
-  # Initialize all local variables with a pattern. This flag will fill uninitialized
-  # floating-point types (and 32-bit pointers) with 0xFF and the rest with 0xAA.
-  # This allows to make behavior of uninitialized memory bugs consistent, easier to
-  # recognize when debugging and often just to crash immediately.
-  init_stack_vars = is_linux && !is_official_build
+  # Initialize all local variables with a pattern. This flag will fill
+  # uninitialized floating-point types (and 32-bit pointers) with 0xFF and the
+  # rest with 0xAA. This makes behavior of uninitialized memory bugs consistent,
+  # recognizeble in debugger, and crashes memory accesses by uninitialized
+  # pointers.
+  # TODO(vitalybuka): is_win needs next llvm roll.
+  # 'is_android' breaks content_shell_test_apk on android-kitkat-arm-rel.
+  # 'use_xcode_clang' may call old clang.
+  init_stack_vars =
+      !is_android && !is_win && !use_xcode_clang && !is_official_build
 }
 
 declare_args() {