selftests: hid: make vmtest rely on make

Having a default binary is simple enough, but this also means that
we need to keep the targets in sync as we are adding them in the Makefile.

So instead of doing that manual work, make vmtest.sh generic enough to
actually be capable of running 'make -C tools/testing/selftests/hid'.

The new image we use has make installed, which the base fedora image
doesn't.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>