clean up message for OSError errorhandler
clean up message for OSError errorhandler

Currently it repeats the text of the exception, which appeared
immediately above. And strerror is already part of args, so that was
then doubled. `str(e)` formats this much better anyway.

While we are at it, point out that it is probably a build environment
issue, rather than just saying "this is probably not a meson bug". The
former comes across a bit more as constructive advice rather than just
"idk but it's not our fault".

mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,pexip/meson,pexip/meson,pexip/meson,pexip/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson,pexip/meson