Fixes #321 bad paths in wrapper scripts

 - N.B. I think things will break if the user passes `DESTDIR=<...>
   make install` This needs to be made more robust

 - CMake should write one script via `configure_file()` at build time
   into a staging directory that points to the build locations of
   everything and is made a+x

 - CMake should then use `configure_file()` again during `make
   install` so that it can properly handle cases where the user might
   set `DESTDIR=`

Author: zbeekman

src/mpi/CMakeLists.txt

@@ -81,8 +81,8 @@ install(
 )
 file(READ ${CMAKE_CURRENT_SOURCE_DIR}/../extensions/caf-head CAF_HEADER)
 file(WRITE  "${compiler_wrapper}" "${CAF_HEADER}\n")
-file(APPEND "${compiler_wrapper}"  "caf_mod_dir=\"${CMAKE_INSTALL_INCLUDEDIR}/mod\"\n")
-file(APPEND "${compiler_wrapper}"  "caf_lib_dir=\"${CMAKE_INSTALL_LIBDIR}\"\n")
+file(APPEND "${compiler_wrapper}"  "caf_mod_dir=\"${CMAKE_INSTALL_FULL_INCLUDEDIR}/mod\"\n")
+file(APPEND "${compiler_wrapper}"  "caf_lib_dir=\"${CMAKE_INSTALL_FULL_LIBDIR}\"\n")
 file(APPEND "${compiler_wrapper}"  "caf_version=${PROJECT_VERSION}\n")
 if(gfortran_compiler)
   file(APPEND "${compiler_wrapper}"  "link_args='-fcoarray=lib -lcaf_mpi'\n")