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/clang-c/Makefile b/include/clang-c/Makefile
index 5e3522f..98ea719 100644
--- a/include/clang-c/Makefile
+++ b/include/clang-c/Makefile
@@ -1,7 +1,7 @@
-LEVEL = ../../../..
+CLANG_LEVEL := ../..
 DIRS :=
 
-include $(LEVEL)/Makefile.common
+include $(CLANG_LEVEL)/Makefile
 
 install-local::
 	$(Echo) Installing Clang C API include files