This makes it possible to instruct libstd to never touch the signal
handler for `SIGPIPE`, which makes programs pipeable by default (e.g.
with `./your-program | head -n 1`) without `ErrorKind::BrokenPipe`
errors.

If we don't skip these tests, they will fail in CI when `python3 ../x.py
--stage 2 test --host= --target arm-linux-androideabi` runs. The failure
is:

    auxiliary/libsigpipe_utils.so: error: undefined reference to 'signal'