_pyautolib.so is linked with libasan.a if ASAN is used.

BUG=chromium-os:20711
TEST=run autotests under ASAN

Review URL: http://codereview.chromium.org/8065007

git-svn-id: http://src.chromium.org/svn/trunk/src/build@103298 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -1759,7 +1759,8 @@
             # Only in the linux section for now, since ASAN doesn't
             # work on Mac yet.
             'cflags': [
-              '-fasan -w',
+              '-fasan',
+              '-w',
             ],
             'ldflags': [
               '-fasan',