[release] Fixes setting of module path for installed package.

Previously the module path was a relative to the install
directory. With this patch the CMake package configuration file contains the
full path and the macros are found.
(cherry picked from commit 2cf8309c7b46f1ac8ae1e3554dc0d7d57498b6a5)

Signed-off-by: Markus Blatt <markus@dr-blatt.de>