cmTarget: Do not mistake a preceding error for a CMP0049 failure

After calls to ProcessSourceItemCMP0049, check for an empty return
string to detect a failure instead of trusting GetErrorOccuredFlag.
The latter could have been left from a preceding non-fatal error.

Extend the RunCMake.Configure test to cover a case that exposed this
problem.
Merge topic 'fix-CMP0049-extra-error' into next

8669a33e cmTarget: Do not mistake a preceding error for a CMP0049 failure
Tests/RunCMake/Configure: Order tests alphabetically
Merge topic 'fix-CMP0049-extra-error' into next

ab44c8c3 Tests/RunCMake/Configure: Order tests alphabetically
cmTarget: Do not mistake a preceding error for a CMP0049 failure

After calls to ProcessSourceItemCMP0049, check for an empty return
string to detect a failure instead of trusting GetErrorOccuredFlag.
The latter could have been left from a preceding non-fatal error.

Extend the RunCMake.Configure test to cover a case that exposed this
problem.
Merge topic 'fix-CMP0049-extra-error' into next

b2282631 cmTarget: Do not mistake a preceding error for a CMP0049 failure