Fix run_command() with command on a different drive
Fix run_command() with command on a different drive

On Windows, program on a different drive than srcdir won't have
an expressible relative path; cmd_path will be absolute instead and
shouldn't get added into build_def_files.

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