Build: Fix cmake test runner, so it knows when tests fail

The CMake runner looks at the return code if you don't set
the pattern. Since the AK test suite setup doesn't use return
codes, we were missing test failures.

AK/Tests/CMakeLists.txt

@@ -9,4 +9,11 @@ foreach(source ${AK_TEST_SOURCES})
         COMMAND ${name}
         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
     )
+
+    set_tests_properties(
+        ${name}
+        PROPERTIES
+            FAIL_REGULAR_EXPRESSION
+            "FAIL"
+    )
 endforeach()