msetup: Give a nice error message if cmd_line.txt cannot be read
msetup: Give a nice error message if cmd_line.txt cannot be read

As would happen if someone tried to manually call meson --wipe on a
directory configured with a version < 0.49.0

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