Currently we hardcode "gcc", which means we get a bogus result any time
a non-default CC is passed to Make. In fact, it's bogus even when CC is
not explicitly set, since Make's default is "cc", which isn't
necessarily the same as "gcc".
Fix the issue by passing the compiler to use to check-reallocarray.sh.
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
