Fix clang dependency on llvm.

Change-Id: Ifcd4e0d12e3dfd0546c6569a000e3f42dcfb15e7
diff --git a/clang-host-build.mk b/clang-host-build.mk
index d7b70bb..df3a759 100644
--- a/clang-host-build.mk
+++ b/clang-host-build.mk
@@ -9,6 +9,9 @@
 	$(CLANG_ROOT_PATH)/include	\
 	$(LOCAL_C_INCLUDES)
 
+LLVM_ROOT_PATH := external/llvm
+include $(LLVM_ROOT_PATH)/llvm.mk
+
 ifneq ($(LLVM_HOST_BUILD_MK),)
 include $(LLVM_HOST_BUILD_MK)
 endif