Relative path in CPPFLAGS and distcheck

[Robert Lowe]

Hi!

I have a set of common headers files in includes/ and the following
line in configure.ac:

AC_SUBST(CPPFLAGS,[-I../includes])

...since all source files are in parallel directories.  This works
fine for everything but a distcheck.  Is there a simple means of
placing an absolute path there?  I've tried a couple of different
methods, but no luck.

Also, is it perfectly legit to list these files in the top-level
Makefile.am as EXTRA_DIST, rather than explicitly listing this
subdirectory, adding a Makefile.am there, ... since there's
nothing to build there?

TIA,
Robert