[oe] altering cflags for autotools

[Tobias Pflug]

hi..

today i've been trying to package mod_python but had some difficulties
because ${STAGING_INCDIR} was not included in the path thus
mod_include.h (staged from the apache2 package) could not be found ->
can't compile mod_python.

Changing CFLAGS or EXTRA_CFLAGS has no effect. Looking at the autotools
class that is no surprise because it doesn't seem to be read anywhere. 
How can I fix this? Do I have to patch the configure.in file ? 

Which leads me to my next, slightly related question. When in a devshell
session, shouldn't STAGING_INCDIR be set as environment variable ?

regards,
Tobi