Disable sanitizers with a blacklist.

We think this might be more flexible.  It allows, e.g, function-level blacklisting,
and here an easy one-stop-shop blacklist for all of third_party/externals.

BUG=skia:

CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Debug-ASAN-Trybot
NOTREECHECKS=true

Review URL: https://codereview.chromium.org/1509733003
diff --git a/gyp/common_conditions.gypi b/gyp/common_conditions.gypi
index 7a03f64..ddfd1d3 100644
--- a/gyp/common_conditions.gypi
+++ b/gyp/common_conditions.gypi
@@ -435,8 +435,10 @@
           # Enable asan, tsan, etc.
           [ 'skia_sanitizer', {
             'cflags': [
-              '-fsanitize=<(skia_sanitizer)',
-              '-fno-sanitize-recover=<(skia_sanitizer)',
+              '-fsanitize=<(skia_sanitizer)',                     # Turn on sanitizers.
+              '-fno-sanitize-recover=<(skia_sanitizer)',          # Make any failure fatal.
+              '-fsanitize-blacklist=<(skia_sanitizer_blacklist)', # Compile in our blacklist.
+              '-include <(skia_sanitizer_blacklist)',             # Make every .cpp depend on it.
             ],
             'ldflags': [
               '-fsanitize=<(skia_sanitizer)',