Only build oclgl tests if OpenGL is installed on the system

Change-Id: I226f2e09c98a970ce8dce0b6f670ca13d868aeb6

opencl/tests/ocltst/module/runtime/CMakeLists.txt

@@ -61,9 +61,14 @@ target_include_directories(oclruntime
 
 target_link_libraries(oclruntime
     PRIVATE
-        OpenCL
-        ${GLEW_LIBRARIES}
-        ${OPENGL_LIBRARIES})
+        OpenCL)
+
+if(OPENGL_FOUND AND GLEW_FOUND)
+    target_link_libraries(oclruntime
+        PRIVATE
+            ${GLEW_LIBRARIES}
+            ${OPENGL_LIBRARIES})
+endif()
 
 add_custom_command(
     TARGET oclruntime POST_BUILD