experimental/cmake-improvement

set CMAKE_LIBRARY_PATH, CMAKE_INCLUDE_PATH based on NIX_CFLAGS_COMPILE and
NIX_LDFLAGS so that cmake's find_library like functions find all the libraries
gcc knows about thanks to the gcc wrapper

This is particular useful with myEnvFun which then also sets those CMAKE_* env
variables.`

Because setup.sh has to change this causes many rebuilds - thus it should be
included in a stdenv-update like branch

Also cmake builds in parallel perfectly fine