Setting compiler flags via AC_ARG_WITH in configure.in

[Markus Werle]

Hi!

This is my first attempt to use the GNU auto-toolkit
for my own project, and I found this rather hard to achieve
(the cross-directory support is somehow not as developed as
expected ...)

Now I deal with another problem: I want to set include paths
during configure run, e.g. --with-loki=/path/to/loki
The following code works fine, but I feel unhappy about the
use of an external environment variable.

Now I am tired reading the docs (20 hours at least).
Please enlighten me and improve on this snippet

AC_ARG_WITH(loki,
    [  --with-loki=LOKI_PREFIX
                          place where loki headers reside ],
    [ export CXXFLAGS="-I$withval $CXXFLAGS"])


Thanks,

Markus