compilers: fix type issue
compilers: fix type issue

mesonlib.darwin_get_object_archs() only accepts a string argument so convert
it.

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