leveldb: Add correct CFLAGS

leveldb does not respect custom's CFLAGS.
This CL fix this.

BUG=None
TEST=The CFLAGS is added.

Change-Id: I7ce1c49d757899723811740cc8713ad57f4127f9
Reviewed-on: https://chromium-review.googlesource.com/179378
Reviewed-by: Han Shen <[email protected]>
Reviewed-by: Caroline Tice <[email protected]>
Tested-by: Yunlian Jiang <[email protected]>
Reviewed-by: Mike Frysinger <[email protected]>
Commit-Queue: Yunlian Jiang <[email protected]>
1 file changed