gitweb tests: skip tests when we don't have Time::HiRes

Change the gitweb tests to skip when we can't load the Time::HiRes
module.

Gitweb needs this module to work. It has been in perl core since v5.8,
which is the oldest version we support. However CentOS (and perhaps
some other distributions) carve it into its own non-core-perl package
that's not installed along with /usr/bin/perl by default. Without this
we'll hard fail the gitweb tests when trying to load the module.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/gitweb-lib.sh

@@ -114,4 +114,9 @@ perl -MCGI -MCGI::Util -MCGI::Carp -e 0 >/dev/null 2>&1 || {
 	test_done
 }
 
+perl -mTime::HiRes -e 0 >/dev/null 2>&1 || {
+	skip_all='skipping gitweb tests, Time::HiRes module not available'
+	test_done
+}
+
 gitweb_init