cmake: --build -j <jobs> should not accept 0
When trying to disable parallel builds for a GHS project I used
cmake --build . -j 0 thinking the build command line to be
gbuild --parallel=0 to disable the default parallel builds mode of
gbuild. However 0 is reserved as the tool default value so the command line was
gbuild --parallel. Since 0 is reserved and 1 should suffice to limit to one process then CMake probably shouldn't accept a value of zero.