When adding a new directory to the Mozilla codebase, one usually needs to add a Makefile.in file, with some magic incantations at the beginning of it:
DEPTH = ../.. topsrcdir = @top_srcdir@ srcdir = @srcdir@ VPATH = @srcdir@ include $(DEPTH)/config/autoconf.mk etc.
Some even add:
relativesrcdir = foo/bar
In the above, DEPTH and relativesrcdir both need to be carefully filled depending where the Makefile.in is.
As of bug 774032, landed over the week-end (along with some now hopefully fixed tree breakage for some people, sorry for the inconvenience), there are two additional substitution variables for Makefile.in that replace the need to be careful.
Now the boilerplate for a new Makefile.in is:
DEPTH = @DEPTH@ topsrcdir = @top_srcdir@ srcdir = @srcdir@ VPATH = @srcdir@ include $(DEPTH)/config/autoconf.mk etc.
And, if needed,
relativesrcdir = @relativesrcdir@