Makes the test suite run in src_test(), not src_compile(). Note that
at the moment all the output from the test runner goes into the CTest log
and all that src_test() shows is the overall status of the execution
of the runner.

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,8 +1,6 @@
 cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
 
-if (NOT DEFINED RUN_TEST_SUITE)
-option (RUN_TEST_SUITE "run test suite after install" ON)
-endif (NOT DEFINED RUN_TEST_SUITE)
+include(CTest)
 
 add_subdirectory(Source/GmmLib)
 
--- a/Source/GmmLib/CMakeLists.txt
+++ b/Source/GmmLib/CMakeLists.txt
@@ -495,7 +495,7 @@
 		_X64)
 endif()
 
-if(NOT DEFINED RUN_TEST_SUITE OR RUN_TEST_SUITE)
+if(BUILD_TESTING)
     add_subdirectory(ULT)
 endif()
 
--- a/Source/GmmLib/ULT/CMakeLists.txt
+++ b/Source/GmmLib/ULT/CMakeLists.txt
@@ -151,9 +151,7 @@
 
 add_custom_target(Run_ULT ALL DEPENDS GMMULT)
 
-add_custom_command(
-    TARGET Run_ULT
-    POST_BUILD
-    COMMAND echo running ULTs
+add_test(
+    NAME Run_ULT
     COMMAND "${CMAKE_COMMAND}" -E env "LD_LIBRARY_PATH=$<TARGET_FILE_DIR:igfx_gmmumd_dll>" ${CMAKE_CFG_INTDIR}/${EXE_NAME} --gtest_filter=CTest*
 )