MFC r279980:

MFC r279980:

Allow relative pathnames in SRCS, so as to enable building software
which includes more than one file with the same name, in different
directories.

For example, setting:

SRCS+=	foo/foo.c bar/foo.c baz/foo.c

will now create separate objdirs 'foo', 'bar' and 'baz' for each of the
sources in the list, and use those objdirs for the corresponding object
files.

Reviewed by:	brooks, imp
Differential Revision: https://reviews.freebsd.org/D1984

git-svn-id: svn://svn.freebsd.org/base/stable/9@280329 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f