tests/util/grub-shell: Print gdbinfo if on EFI platform

Allow using GDB to debug a failing QEMU test. This output does not cause
issues for tests because it happens before the trim line, and so will be
ignored.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

tests/util/grub-shell.in

@@ -360,6 +360,9 @@ halt_cmd=${halt_cmd}
 export halt_cmd
 enable_progress_indicator=0
 export enable_progress_indicator
+if [ "${grub_modinfo_platform}" == efi ]; then
+  gdbinfo
+fi
 EOF