We were doing this on the basis of an old comment, but there was no
test for it and I couldn't reproduce the issue with clang on Linux
at all.
Let's add a (somewhat comprehensive) test and see if it breaks
anywhere if we stop doing this.
Halves the size of gstreamer's build.ninja from 20M to 8.7M
Closes https://github.com/mesonbuild/meson/issues/1057
Nirbheek Chauhan