Exclude debuginfo files from "outside of ELF segments" warning

Exclude debuginfo files from "outside of ELF segments" warning

When GDB loads an ELF file, it will warn when a section is not located
in an ELF segment:

$ ./gdb -q -iex "set build-id-verbose 0" --ex "b systemctl_main" -ex "r" -batch --args systemctl kexec
Breakpoint 1 at 0xc24d: file ../src/systemctl/systemctl.c, line 8752.
warning: Loadable section ".note.gnu.property" outside of ELF segments
  in .gnu_debugdata for /lib64/libgcc_s.so.1
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
warning: Loadable section ".note.gnu.property" outside of ELF segments
  in .gnu_debugdata for /lib64/libcap.so.2
warning: Loadable section ".note.gnu.property" outside of ELF segments
  in .gnu_debugdata for /lib64/libacl.so.1
warning: Loadable section ".note.gnu.property" outside of ELF segments
  in .gnu_debugdata for /lib64/libcryptsetup.so.12
warning: Loadable section ".note.gnu.property" outside of ELF segments
  in .gnu_debugdata for /lib64/libgcrypt.so.20
warning: Loadable section ".note.gnu.property" outside of ELF segments
  in .gnu_debugdata for /lib64/libip4tc.so.2
[snip]
This has feature has also been reported by various users, most notably
the Fedora-EOL'd bug 1553086.

Mark Wielaard explains the issue quite nicely in

   https://sourceware.org/bugzilla/show_bug.cgi?id=24717#c2

The short of it is, the ELF program headers for debuginfo files are
not suited to this particular use case. Consequently, the warning
generated above really is useless and should be ignored.

This patch follows the same heuristic that BFD itself uses.

gdb/ChangeLog
2020-11-13  Keith Seitz  <keiths@redhat.com>

	https://bugzilla.redhat.com/show_bug.cgi?id=1553086
	* elfread.c (elf_symfile_segments): Omit "Loadable section ...
	outside of ELF segments" warning for debugin