cccl: Enable ability to parallel build.

The /FS option allows serial access to PDB file creation letting
parallel builds succeed with mingw32-make (with some tricks). The
'make' that comes with MSYS has a bug that causes hangs with
parallel builds which supposedly has been fixed in the upcoming
1.0.19 release.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Saurabh Shah <ssaurabh@vmware.com>