* lib/gdb.exp (build_id_debug_filename_get): New function.

	* lib/gdb.exp (build_id_debug_filename_get): New function.
	* gdb.base/sepdebug.exp: Reflect the changes in the heading comment.
	Remove the generate DEBUG file for the future testcase runs.
	New testcase for the NT_GNU_BUILD_ID retrieval.
	Move the final testing step to ...
	(test_different_dir): ... a new function.
	New parameter XFAIL to XFAIL all the tests performed.
	New parameter TEST_DIFFERENT_DIR parametrizing the directory.
	New parameter TYPE to PF_PREFIX all the tests performed.