sim: testsuite: fix cris stat3 in diff setups

sim: testsuite: fix cris stat3 in diff setups

This test uses the test itself as an input to stating regular files.
This gets funky though: when we run check in parallel, the output
object dir is the subdir that matches the .exp file.  When we run
with -j1, the output object dir is the sim builddir itself.

The old test would append argv[0] to find the file, while the new
test uses basename on it.  Each method works in only one of the
aforementioned build scenarios.  Rather than complicate this any
more, switch to a different file that we know will always exist:
the Makefile.