Use find_package instead of include.

rdar://27062396

Author: gottesmm

cmake/modules/SwiftSharedCMakeConfig.cmake

@@ -34,7 +34,8 @@ macro(swift_common_standalone_build_config_llvm product is_cross_compiling)
 
   # Then we import LLVMConfig. This is going to override whatever cached value
   # we have for LLVM_ENABLE_ASSERTIONS.
-  include(LLVMConfig)
+  find_package(LLVM REQUIRED CONFIG
+    HINTS "${PATH_TO_LLVM_BUILD}" NO_DEFAULT_PATH)
 
   # If we did not have a cached value for LLVM_ENABLE_ASSERTIONS, set
   # LLVM_ENABLE_ASSERTIONS_saved to be the ENABLE_ASSERTIONS value from LLVM so
@@ -128,10 +129,9 @@ macro(swift_common_standalone_build_config_clang product is_cross_compiling)
     list(APPEND CMAKE_MODULE_PATH ${path})
   endforeach()
 
-  # Then include ClangTargets.cmake. If Clang adds a ClangConfig.cmake, this is
-  # where it will be included. By including ClangTargets.cmake, we at least get
-  # the right dependency ordering for clang libraries.
-  include(ClangTargets)
+  # Then include Clang.
+  find_package(Clang REQUIRED CONFIG
+    HINTS "${PATH_TO_CLANG_BUILD}" NO_DEFAULT_PATH)
 
   if(NOT EXISTS "${PATH_TO_CLANG_SOURCE}/include/clang/AST/Decl.h")
     message(FATAL_ERROR "Please set ${product}_PATH_TO_CLANG_SOURCE to the root directory of Clang's source code.")