build: check for unexpanded macros in configure.ac
build: check for unexpanded macros in configure.ac

We're now using m4 macros from the autoconf-archive collection. The
user may be missing this package so check for unexpanded AX_* macros
and bail-out if any are found.

Signed-off-by: Bartosz Golaszewski <108de5fbc428215dc26df4468b48691526611148@gmail.com>

brgl/libgpiod,brgl/libgpiod,brgl/libgpiod,brgl/libgpiod