For PR automake/500: * automake.in (handle_compile) <$default_includes>: Do not output the same -I twice. Use @am__isrc@ instead of ` -I$(srcdir)'. * m4/init.m4: Define am__isrc as ` -I$(srcdir)' only in non-VPATH builds since we always have `-I.'. * tests/subpkg.test: Make sure config headers are found in VPATH and non-VPATH builds.