debug: Autogenerate _FORTIFY_SOURCE tests

Rename debug/tst-chk1.c to debug/tst-fortify.c and add make hackery to
autogenerate tests with different macros enabled to build and run the
same test with different configurations as well as different
fortification levels.

The change also ends up expanding the -lfs tests to include
_FORTIFY_SOURCE=3.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>