Allow to configure more dirs

[agx]

These patches allow to:

• add a ${DESTDIR}. This is needed for distro packaging where you install into /whatever/build/dir/usr/lib/libgovarnam.so.1.9.0 but want the path on the installed system to be /usr/lib/libgovarnam.so.1.9.0.
• alllow to set libdir. This is needed for multiarch installs where you want the libs to be in `/usr/lib//libvarnam.so.1.9.0
• allow to skip the cli install (for the case where it's not built)
• instead of changing the files via sed multiple times we use one call. In order to avoid problems when running out of diskspace we create a temp file and move that into place.

With these I can build a policy conformant library package for Debian.