Makefile: Switch Clang Makefiles to always include the top-level Clang Makefile.
 - This eliminates most dependencies on how Clang is installed relative to LLVM.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@105637 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/Makefile b/include/Makefile
index f686d6a..79b9adf 100644
--- a/include/Makefile
+++ b/include/Makefile
@@ -1,4 +1,4 @@
-LEVEL = ../../..
+CLANG_LEVEL := ..
 DIRS := clang clang-c
 
-include $(LEVEL)/Makefile.common
+include $(CLANG_LEVEL)/Makefile