Add call to find_package to load LLVM dependencies

ClangConfig requires LLVMConfig, so add find_package call in
ClangConfig so find_package(clang REQUIRED CONFIG) will just work.  This
makes it easier for cmake based projects to use clang, e.g., tools using
ClangTooling.

Patch by Don Hinton

Differential Revision: http://reviews.llvm.org/D13622

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@261290 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/ClangConfig.cmake

@@ -4,5 +4,7 @@
 # uses LLVM's. When it does, we should move this file to ClangConfig.cmake.in
 # and call configure_file() on it.
 
+find_package(LLVM REQUIRED CONFIG)
+
 # Provide all our library targets to users.
 include("${CMAKE_CURRENT_LIST_DIR}/ClangTargets.cmake")