testsuite: Remove cmp-1-2-long.txt in "make clean"

It's generated by "make check".

For the "retry failed tests" work, I've been doing some changes to the
compare_dg_tests.pl script. In the process I made some cleanups, and also
the KFAIL support in the last patch in this series that I will need for the
GDB testsuite.

Change-Id: I55540a3ecc1862c3d2162e48e94d3e8eff6fd7ac
1 file changed