Add make regress support and pass through cleandepend via bsd.progs.mk

make regress is effectively a shortcut for make
test on target machines using binaries in ${.OBJDIR}.

Also, invoke test call via env TESTS_ENV, not TESTS_ENV bareword

Signed-off-by: Garrett Cooper <yanegomi@gmail.com>
Merge branch 'master' of github.com:/yaneurabeya/freebsd
Merge branch 'master' of github.com:/yaneurabeya/freebsd