build.sh: forward make arguments to mixed GKI builds

Pass along any given command line arguments to the mixed GKI builds
running in a subshell. This allows using options such as silent mode or
overriding the number of jobs which is currently fixed via MAKEFLAGS.
Example:

  $ ./build/build.sh -s -j1

Signed-off-by: Carlos Llamas <cmllamas@google.com>
Change-Id: I6a8e2b1474fc3007c9c2d689cc7449ac23e378f6
1 file changed