AOSP: Use '-Os' rather than '-Oz'

Cuttlefish recently hit a clang compiler issue related to -Oz:
  b/200617543

This is fixed by either disabling optimizations for ScopedExit or using
-Os.

This CL will switch ANGLE to using -Os.

When building CF in AOSP, the binary size is reduced with -Os vs -Oz:
  -Oz: 16,383,489 bytes
  -Os: 16,152,509 bytes

Bug: b/200617543
Change-Id: Ic920b0e0e4a61453d9657101a4560f74d90d5744
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3253128
Reviewed-by: Jason Macnak <natsu@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Tim Van Patten <timvp@google.com>

scripts/generate_android_bp.py

@@ -290,7 +290,7 @@ def gn_cflags_to_blueprint_cflags(target_info):
     result.append('-Wno-unknown-warning-option')
 
     # Override AOSP build flags to match ANGLE's CQ testing and reduce binary size
-    result.append('-Oz')
+    result.append('-Os')
     result.append('-fno-unwind-tables')
 
     if 'defines' in target_info: