Make gmock dep initially not required

Add a 'required: false' when building the gmock dependency so it doesn't
have to be present initially, as the code right below will already fetch
it if not present.  Otherwise, the build will fail before it has a
chance to build the subproject if it needs it.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I20c58f3b5b6978fa6deb69cdf799e34bb4054ce4
1 file changed