Don't attempt to run llvm-config in cmake/modules/Makefile when doing

``make clean`` because it won't be available.

This is an attempt to unbreak buildbots broken by r217484.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217490 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/Makefile

@@ -33,6 +33,8 @@ else
 	LLVM_ENABLE_RTTI := 0
 endif
 
+# Don't try to run llvm-config during clean because it won't be available
+ifneq ($(MAKECMDGOALS),clean)
 LLVM_LIBS_TO_EXPORT := $(subst -l,,$(shell $(LLVM_CONFIG) --libs $(LINK_COMPONENTS) || echo Error))
 
 ifeq ($(LLVM_LIBS_TO_EXPORT),Error)
@@ -42,6 +44,7 @@ endif
 ifndef LLVM_LIBS_TO_EXPORT
 $(error LLVM_LIBS_TO_EXPORT cannot be empty)
 endif
+endif
 
 OBJMODS := LLVMConfig.cmake LLVMConfigVersion.cmake LLVMExports.cmake