Add if(POLICY)
Merge topic 'target-LOCATION-policy' into next

eedb98d Add if(POLICY)
cmTarget: Deprecate the LOCATION target property with a policy.

The final location and name of a build-target is not determined
until generate-time. However, reading the LOCATION property from
a target is currently allowed at configure time. Apart from creating
possibly-erroneous results, this has an impact on the implementation
of cmake itself, and prevents some major cleanups from being made.

Disallow reading LOCATION from build-targets with a policy. Port some
existing uses of it in CMake itself to use the TARGET_FILE generator
expression.
Merge topic 'target-LOCATION-policy' into next

352f2c3 cmTarget: Deprecate the LOCATION target property with a policy.