precompiled headers and -I- resp. iquote

[Ralf Wildenhues <Ralf dot Wildenhues at gmx dot de>]

While pondering possible gch support in libtool, the deprecation of
-I- makes me wonder about intended use:

Say I have two precompiled headers for ./foo.h,
  .libs/pic/foo.h.gch
with -fPIC -DPIC and
  .libs/nopic/foo.h.gch
without.

I do not see a way of using them for ./bar.c without -I-, since even
-iquote .libs/... will still prefer ./foo.h.  Will there be a
replacement switch to insert paths before the source file directory?
If not, what is the rationale?

(The directory names shown are still subject to discussion.)

Thanks for any hints,
Ralf