do not use Executor if only one process was requested
do not use Executor if only one process was requested

This will make verbose output nicer, since it will not interleave the test
stdout/stderr and the test results.

becm/meson,mesonbuild/meson,becm/meson,QuLogic/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,becm/meson,jpakkane/meson,becm/meson,pexip/meson,pexip/meson,jpakkane/meson,becm/meson,jpakkane/meson,mesonbuild/meson,becm/meson,mesonbuild/meson,pexip/meson,pexip/meson,QuLogic/meson,becm/meson,becm/meson,jpakkane/meson,becm/meson,pexip/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,mesonbuild/meson,becm/meson,jpakkane/meson,pexip/meson,QuLogic/meson,pexip/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,pexip/meson,QuLogic/meson,mesonbuild/meson