configuring apps for guile

[Matt Wette <matt.wette@gmail.com>]

Hi All,

Over the last year I have been dealing with issues getting a 
configure.ac put together
for my guile app.  It needs to install .scm and .go files into the place 
guile expects to
see them: (%site-ccache-dir) and %load-path.   If I compile for my 
ubuntu system then
the installed go files need to go in a non-standard place:
   /usr/lib/x86_64-linux-gnu/guile/2.2/site-ccache
If I compile for the guix context then the expectation is that the files 
are installed in
  $prefix/lib/guile/2.2/site-ccache

Here is my solution.  What do you think?  If $prefix is the same as used 
to build guile
then I use the directories from $guile.  Otherwise, I use the default.  
This now works on
ubuntu and guix.

 From configure.ac:

guile_build_prefix=`$GUILE -c "(display (assq-ref %guile-build-info 
'prefix))"`

if test "$guile_build_prefix" == "$prefix"; then
   echo "using paths for installed guile"
   GUILE_SITE_DIR
   GUILE_SITE_GO_DIR
   GUILE_DATA_DIR
else
   echo "using default paths for guile"
   GUILE_SITE=$prefix/share/guile/site/$GUILE_EFFECTIVE_VERSION
GUILE_SITE_GO=$prefix/lib/guile/$GUILE_EFFECTIVE_VERSION/site-ccache
   GUILE_DATA=$prefix/share
   AC_SUBST([GUILE_SITE])
   AC_SUBST([GUILE_SITE_GO])
   AC_SUBST([GUILE_DATA])
fi

GUILE_SITE_DIR is defined in guile.m4, the others are in my own package m4.