Merge topic 'external-language-compiler-id'

e65c788 CMakeDetermineCompilerId: Load src from CMAKE_MODULE_PATH (#14481)

Modules/CMakeDetermineCompilerId.cmake

@@ -85,7 +85,9 @@ endfunction()
 #-----------------------------------------------------------------------------
 # Function to write the compiler id source file.
 function(CMAKE_DETERMINE_COMPILER_ID_WRITE lang src)
-  file(READ ${CMAKE_ROOT}/Modules/${src}.in ID_CONTENT_IN)
+  find_file(src_in ${src}.in PATHS ${CMAKE_ROOT}/Modules ${CMAKE_MODULE_PATH} NO_DEFAULT_PATH)
+  file(READ ${src_in} ID_CONTENT_IN)
+  unset(src_in CACHE)
   string(CONFIGURE "${ID_CONTENT_IN}" ID_CONTENT_OUT @ONLY)
   file(WRITE ${CMAKE_${lang}_COMPILER_ID_DIR}/${src} "${ID_CONTENT_OUT}")
 endfunction()