[gdb/testsuite] Add aranges to gdb.dwarf2/dw2-dir-file-name.exp

Since commit 52b920c5d20 ("[gdb/testsuite] Fix gdb.dwarf2/dw2-dir-file-name.exp
for ppc64le"), the test-case fails with target board cc-with-debug-names, due
to missing .debug_aranges info.

Add the missing .debug_aranges info.

Also add a file_id option to Dwarf::assemble, to make it possible to contribute
to an already open file.

Tested on x86_64-linux.
2 files changed