Access to LOCATION property at config time was disallowed by this
policy. This patch updates the offending code to comply with the policy
and thereby gets rid of the warning printed by cmake.
The fix is to use generator expressions instead of that property.
NOTE: Had to remove support for multiconfig (only affects MSVC which is
not supported anyway; and mutliconf is an IDE thing in any case),
because could not see how to support it with generator expressions.
