build: Fix accidental revert of .gnulib update

Commit id 1bff5bbe accidentally
reverted .gnulib back to d6397dde2e127e246e3eeb5254a21f42cac783c8
which was two updates ago.

Update to the latest 68df637b5f1b5c10370f6981d2a43a5cf74368df
which includes three changes since the previous fetch of
cdbf3d385a32ff904c96f20c26f3470bd8345248.

> autoupdate
> hard-locale: simplify by removing hard-locale.m4
> gnulib-tool: limit line length for git send-email
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

.gnulib @ 68df637b

-Subproject commit d6397dde2e127e246e3eeb5254a21f42cac783c8
+Subproject commit 68df637b5f1b5c10370f6981d2a43a5cf74368df