These policies should be checked at the call site that tries to access
the LOCATION or SOURCES property, not the directory scope containing the
target. Thread the caller context through cmTarget::GetProperty to use
for checking the policy setting and emitting a diagnostic with proper
backtrace.
Extend the RunCMake.CMP0026 and RunCMake.CMP0051 tests with
cross-directory cases.
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.