Commit c408fa88a3 introduced changes
to the BUILD_ASSERT() macro so the MSG argument is optional.
However, in include/toolchain/common.h, the BUILD_ASSERT()
definition has not made the MSG argument as optional which results
in build errors complaing about too few arguments. Fix by adding
some dots there.
This is observed when using XCC (based on Clang 3.9).
Fixes#24008
Signed-off-by: Daniel Leung <daniel.leung@intel.com>