Test ERT for a newer API level

We use an ERT version which needs to know whether at least this
function signature exists. The earlier implementation covers too
many versions.
Special handling for some recognized env. vars.

CMake does not like that you specify the compiler with the environment
variables, instead preferring that you set them as cache variables.
This layer translate between the names of the the two.
Mimic Autotools way to specify non-standard Boost

If Boost is installed in say /usr/include/boost141 and
/usr/lib64/boost141, then there is no root you can specify to pick
them both up. However, whereas Autotools uses --with-boost and
--with-boost-libdir, FindBoost in CMake changes to using two different
variables: BOOST_INCLUDEDIR and BOOST_LIBRARYDIR. Using the header
directory for BOOST_ROOT will not work (in particularily not with
old CMake versions).
Noarch lib-dir was only used in one wrong place

dune.module does not contain any paths to architecture-specific
binaries. It is therefore always installed in no-arch lib/ directory.
Thus, there is no need to have a variable for this, and there was
no other users of this variable either.
Always search for dune.module in no-arch lib-dir

The previous version may have ended up in lib64/ instead of lib/;
now we remove the arch-specific suffix from the path, and always
use the no-arch version.
Print version number in log together with location