Temporarily disable autovectorization in core for 32-bit Linux builds.

BUG=skia:2575
R=rmistry@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/354833006

gyp/core.gyp

@@ -31,6 +31,11 @@
       ],
       'msvs_disabled_warnings': [4244, 4267,4345, 4390, 4554, 4800],
       'conditions': [
+        [ 'skia_arch_type == "x86"', {
+          # GCC autovectorization makes some GMs flaky on 32-bit release builds.
+          # skbug.com/2575.   This bug is likely somewhere here in src/core.
+          'cflags': [ '-fno-tree-vectorize' ]
+        }],
         [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "chromeos"]', {
           'link_settings': {
             'libraries': [