CTestCustom: ignore coverage results from coverage tests

CTestCustom.cmake.in

@@ -126,6 +126,9 @@ list(APPEND CTEST_CUSTOM_COVERAGE_EXCLUDE
 
   # Exclude Qt source files from coverage results:
   "[A-Za-z]./[Qq]t/qt-.+-opensource-src"
+
+  # Exclude coverage results from coverage test directories.
+  "/Testing/.*Coverage/"
   )
 
 list(APPEND CTEST_CUSTOM_MEMCHECK_IGNORE