* tests/scripts/features/archives: Handle deterministic archives.

* tests/scripts/features/archives: Handle deterministic archives.

Newer versions of binutils allow ar to be compiled to generate
"deterministic archives" by default: in this mode no timestamp
information is generated in the static archive, which utterly
breaks GNU make's archive updating capability.  Debian and Ubuntu
have turned this feature on by default in their distributions
which causes the regression tests to fail.

Update the regression tests to check for the availability of the
"U" option to ar which disables deterministic archives and allows
GNU make's archive support to work properly again.