It seems like it was never really needed as we always delete the archive
before creating it anyhow and there is no advantage in "updating" it if it
doesn't exist. Worse, with recent ar versions (like the one from binutils 2.25
in Debian Sid), using "u" results in a somewhat unclear warning
ar: `u' modifier ignored since `D' is the default (see `U')
so just get rid of it to avoid the warning.
(cherry picked from commit 004b5a4f49)
90cec63a53