Use buildutil directory within fplutil.
Use buildutil directory within fplutil.

Before, including cmake_common.txt was not working when staging
for GitHub push because the include was using ${fplroot}, which
directed it to fplutil/dependencies/fplutil/buildutil. This causes
a CMake error; we should just be using fplutil/buildutil.

Tested:
Works on OS X

Change-Id: Ib741efc2722cbbf8455d081f053cd82a394c17dc

google/fplutil,google/fplutil,google/fplutil,google/fplutil,google/fplutil,google/fplutil