Updated CMAKE_MODULE_PATH (#140)

Summary:
When wangle is embedded as subdirectory, CMAKE_SOURCE_DIR will point to the root project instead of wangle. Using CMAKE_CURRENT_SOURCE_DIR to make sure cmake finds correct module files.
Pull Request resolved: #140

Reviewed By: yfeldblum

Differential Revision: D9826260

Pulled By: Orvid

fbshipit-source-id: 509ee49f59096505cd77ab634ec9d06f8b886019

wangle/CMakeLists.txt

@@ -11,7 +11,7 @@ project("wangle" VERSION 1.0.0 LANGUAGES CXX C)
 
 add_compile_options(-std=c++1y)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/)
+set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/)
 
 # When installing Folly & Wangle in a non-default prefix, this will let
 # projects linking against libwangle.so to find libfolly.so automatically.