Contained clang specific pragmas inside #if defined(__clang__) #endif

BUG=none
TEST=cbuildbot --remote lakitu-release builds fine.

Change-Id: Ia1b7df02c5726a44cc9261db492a805f7de7a5a6
Reviewed-on: https://chromium-review.googlesource.com/538921
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/payload_generator/ext2_filesystem.cc b/payload_generator/ext2_filesystem.cc
index ee2f8c2..b884021 100644
--- a/payload_generator/ext2_filesystem.cc
+++ b/payload_generator/ext2_filesystem.cc
@@ -17,12 +17,16 @@
 #include "update_engine/payload_generator/ext2_filesystem.h"
 
 #include <et/com_err.h>
+#if defined(__clang__)
 // TODO: Remove these pragmas when b/35721782 is fixed.
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wmacro-redefined"
+#endif
 #include <ext2fs/ext2_io.h>
 #include <ext2fs/ext2fs.h>
+#if defined(__clang__)
 #pragma clang diagnostic pop
+#endif
 
 #include <map>
 #include <set>