ninjabackend: Fix a couple of rust bugs
ninjabackend: Fix a couple of rust bugs

There are two bugs here, first is that we open coded the output args,
instead of using the compiler method. The second is that rust args are
not passed down to the backend invocation.

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