[cmake] Set IS_DEBUG with asserts enabled

Author: kerbowa

CMakeLists.txt

@@ -16,7 +16,7 @@ if(NOT CMAKE_BUILD_TYPE)
   message(FATAL_ERROR "Must set cmake build type.")
 endif()
 
-if(${PACKAGE_VERSION} VERSION_LESS "7.0")
+if(LLVM_ENABLE_ASSERTIONS)
   add_definitions("-DLLVM_DEBUG=DEBUG")
 endif()