Use PROJECT_SOURCE_DIR instead of CMAKE_CURRENT_SOURCE_DIR where appr…

…opriate (#154)

Resolves #153 (Use PROJECT_SOURCE_DIR instead of
CMAKE_CURRENT_SOURCE_DIR where appropriate).

CMakeLists.txt

@@ -20,5 +20,5 @@ project( toolchain-avr-gcc
     LANGUAGES C CXX
     )
 
-list( APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}" )
+list( APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}" )
 include( avrdude-utilities.cmake )