To save disk space, some distributions strip the debugging information
from the binaries, putting it in separate files, usually distributed in
separate packages.

To locate the file containing the debug information for a certain
binary, an ELF note named ".note.gnu.build-id" is added to the latter,
which contains a header and a build identification. This identification
can be used to compose a path with this form:

/usr/lib/debug/.build-id/BUILDID[:2]/BUILDID[2:].debug

With this patch, if Delve can't find the debug information in the main
binary, it'll try to locate and parse ".note.gnu.build-id", to compose
and attempt to open a path with the format described above.

Fixes #1206