ctest_memcheck: Change failure to find log file from error to warning

Sanitizers do not create a log file when no defects are found. Therefore,
it is currently impossible for ctest_memcheck to set both
`CAPTURE_CMAKE_ERROR` and `RETURN_VALUE` to zero.


With defects, `CAPTURE_CMAKE_ERROR`=0 and `RETURN_VALUE`=-1, as expected.

With no defects, `CAPTURE_CMAKE_ERROR`=-1 and `RETURN_VALUE`=0.

Source/CTest/cmCTestMemCheckHandler.cxx

@@ -1087,7 +1087,7 @@ void cmCTestMemCheckHandler::TestOutputFileNames(
     g.FindFiles(ofile);
     if (g.GetFiles().empty()) {
       std::string log = "Cannot find memory tester output file: " + ofile;
-      cmCTestLog(this->CTest, ERROR_MESSAGE, log << std::endl);
+      cmCTestLog(this->CTest, WARNING, log << std::endl);
       ofile.clear();
     } else {
       files = g.GetFiles();
@@ -1095,7 +1095,7 @@ void cmCTestMemCheckHandler::TestOutputFileNames(
     }
   } else if (!cmSystemTools::FileExists(ofile)) {
     std::string log = "Cannot find memory tester output file: " + ofile;
-    cmCTestLog(this->CTest, ERROR_MESSAGE, log << std::endl);
+    cmCTestLog(this->CTest, WARNING, log << std::endl);
     ofile.clear();
   }
   files.push_back(std::move(ofile));

Tests/RunCMake/ctest_memcheck/DummyAddressLeakSanitizer-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyAddressSanitizer-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyLeakSanitizer-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyLeakSanitizerPrintDefects-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyMemorySanitizer-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyPurifyNoLogFile-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyThreadSanitizer-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyUndefinedBehaviorSanitizer-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyValgrindCustomOptions-result.txt

@@ -1 +0,0 @@
-(-1|255)

Tests/RunCMake/ctest_memcheck/DummyValgrindNoLogFile-result.txt

@@ -1 +0,0 @@
-(-1|255)