Related to PR automake/385: * lib/depcomp (dashmstdout): Do not use `-o /dev/null', or gcc will write dependencies to /dev/null. `-o /dev/null' was added on 2002-06-13 just because I tried to replace `-o foo.o' by something else and didn't thought about removing it entirely. * tests/depcomp3.test: New file. * tests/Makefile.am (TESTS): Add it.