Enable JIT/MCJIT unit tests for targets with JIT support.
Change unittests/ExecutionEngine/Makefile to include Makefile.config before
TARGET_HAS_JIT flag is checked.

Fixes bug: http://llvm.org/bugs/show_bug.cgi?id=15669



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178871 91177308-0d34-0410-b5e6-96231b3b80d8