[CMake] Fix add_llvm_external_project()

[kerberizer]

Summary

r250835 unintentionally discarded the optional parameter to the add_llvm_external_project() macro that may point to a path when the said path is different from ${name}. This should fix it by passing ${ARGN} on to add_llvm_subdirectory(). The problem manifests itself with e.g. add_llvm_external_project(clang-tools-extra extra) from clang/tools/CMakeLists.txt

References:
http://reviews.llvm.org/D13783
http://llvm.org/viewvc/llvm-project?view=revision&revision=250835

[beanz]

LGTM. Thank you for fixing this.

-Chris

[klimek]

Committed in r251001

cmake/modules/AddLLVM.cmake

 endmacro()
 
 # Add external project that may want to be built as part of llvm such as Clang,
 # lld, and Polly. This adds two options. One for the source directory of the
 # project, which defaults to ${CMAKE_CURRENT_SOURCE_DIR}/${name}. Another to
 # enable or disable building it with everything else.
 # Additional parameter can be specified as the name of directory.
 macro(add_llvm_external_project name)
-  add_llvm_subdirectory(LLVM TOOL ${name})
+  add_llvm_subdirectory(LLVM TOOL ${name} ${ARGN})
 endmacro()
 
 macro(add_llvm_tool_subdirectory name)
   add_llvm_external_project(${name})
 endmacro(add_llvm_tool_subdirectory)
 
 function(get_project_name_from_src_var var output)
   string(REGEX MATCH "LLVM_EXTERNAL_(.*)_SOURCE_DIR"