Set DESTDIR and TESTBASE so in-tree testing works as expected
with make check/regress

Signed-off-by: Garrett Cooper <yanegomi@gmail.com>
Add a seatbelt if someone sets SCRIPTS and runs make check/regress

Signed-off-by: Garrett Cooper <yanegomi@gmail.com>
Merge branch 'master' into atf-tools-regression-convert

Conflicts:
	share/mk/bsd.test.mk