fixed build in case of submodule

Author: ksergey

CMakeLists.txt

@@ -19,7 +19,7 @@ if(POLICY CMP0054)
     cmake_policy(SET CMP0054 OLD)
 endif()
 
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
 set(MFAST_MAJOR_VERSION 1)
 set(MFAST_MINOR_VERSION 3)