make: add a target for building pyoxidizer tests on macOS
The resources seem to be embedded inside the binary, but for some reasons they
aren't read there. And since they are embedded, they aren't staged by the build
in the `lib` directory like on Windows. So copy them from the repo. We can
figure out what's going wrong later.
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present