pkgsrc-ing Icinga2: cmake and rpath

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I'm trying to pkgsrc icinga2.
I seem almost finished, but the binary doesn't find its self-provided 
libraries, which are in /usr/pkg/lib/icinga2, not /usr/pkg/lib.
Icinga2 uses cmake, which I barely know.
How do I teach it to use a different rpath? I tried
	CMAKE_ARGS+=	-DCMAKE_INSTALL_RPATH=${PREFIX}/lib/icinga2
with and without
	CMAKE_ARGS+=	-DCMAKE_INSTALL_RPATH_USE_LINK_PATH=FALSE
but it doesn't change anything.