Getting cmake to work with/without conan on macOS, Linux and Windows
seems to be trickier than it should be when dealing with older cmake
versions. Switching to an Ubuntu Xenial image on Travis CI at least
makes it build again.
The update then also eliminates the need to update cmake, clang and
maven, saving quite a bit of build time. A few small tweaks and an
update to the macOS image version reduces some 5 minutes from the macOS
build time.
The minimum required version for cmake needs to be updated, too, but
really only when openssl support is included. So instead of raising the
required version in the CMakeFile I am in favour of simply hoping for
the best.
Signed-off-by: Erik Boasson <eb@ilities.com>
