Bug 338791 Handle debug alt dwz files that are relative to the debug file.

readdwarf3 would only look for alt dwz files using the build-id.
But alt files can be installed relative to the debug (or main) file.
Fix find_debug_file to allow searching of relative files even if
we don't want an ET_REL (rel_ok) file, and pass the build-id to
open_debug_file so it can be checked. Add the debug file path to
_DebugInfoFSM and set it in find_debug_file once opened. Pass the
dbgname or filename as relative file to resolve an altfile in
read_elf_debug_info when we ahava an debugaltlink_escn.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14464 a5019735-40e9-0310-863c-91ae7b9d1cf9
3 files changed