util/docker: Don't try to test-build non-existing crostools target

Change-Id: Id6afbff1fd91744da3ba1d5e3e9aa339c46b29b3
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49984
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

util/docker/coreboot-sdk/Dockerfile

@@ -138,6 +138,5 @@ RUN mkdir -p /tmp/work && \
   make -C coreboot test-tools -j && \
   make -C coreboot test-lint -j && \
   make -C coreboot test-cleanup -j && \
-  make -C coreboot CPUS=$(nproc) crostools && \
   cd && \
   rm -rf /tmp/work/