Currently one would have to pass a `macos` flag explicitly to build on
OSX, but if we replace `macos` with `darwin` this happens automatically.
Signed-off-by: Tom Gundersen <teg@jklm.no>
Our current crypt implmentation requires glibc to be available on the
developer's system. But it is not strictly necessary, because I'd like
to run at least unit tests on mac. This PR makes it possible to compile
and run unit-tests on mac, but it will panic if someone tries to run
osbuild-composer on mac.