fix CMAKE_MODULE_PATH for libnfc as a submodule

This fixes nfc-tools#496

Author: daixtrose

Diff for: CMakeLists.txt

@@ -32,7 +32,7 @@ ADD_DEFINITIONS("-DHAVE_CONFIG_H")
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/include)
 
 # make it easy to locate CMake modules for finding libraries
-SET(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake/modules/")
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake/modules/")
 
 # Options
 option (LIBNFC_LOG "Enable log facility (errors, warning, info and debug messages)" ON)