ctest_memcheck: Do not open empty BC output file name

In cmCTestMemCheckHandler::PostProcessBoundsCheckerTest return early
if the output file name is empty.  We already do this in the similar
cmCTestMemCheckHandler::AppendMemTesterOutput method.
Tests: Move CTestTestMemcheck cases into a RunCMake.CTestMemcheck test

The CTestTestMemcheck test cases all try to check the ctest output with
a regular expression.  They fail intermittently due to ordering of the
portions of the output that come from stdout and stderr being mixed.
Convert all the test cases to use the RunCMake infrastructure to match
stdout and stderr separately.
Tests: Move CTestTestMemcheck tools into Tests/CMakeLib

The dummy memcheck tools we build for the RunCMake.CTestMemcheck tests
require CMakeLib, so put them in a Tests/CMakeLib/PseudoMemcheck
directory.
Merge topic 'test-memcheck-with-RunCMake' into next

a6ee00e6 Tests: Move CTestTestMemcheck tools into Tests/CMakeLib
0e94a59a Tests: Move CTestTestMemcheck cases into a RunCMake.CTestMemcheck test
1c812979 ctest_memcheck: Do not open empty BC output file name