t9500: skip gitweb tests if perl version is too old

gitweb calls Encode::decode_utf8 with two arguments,
but old versions of perl only allow this function to be called
with one argument.  Even older versions of perl do not even
have an Encode module.
Signed-off-by: NSven Verdoolaege <skimo@kotnet.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t9500-gitweb-standalone-no-errors.sh

@@ -60,6 +60,12 @@ gitweb_run () {
 
 . ./test-lib.sh
 
+perl -MEncode -e 'decode_utf8("", Encode::FB_CROAK)' >/dev/null 2>&1 || {
+    test_expect_success 'skipping gitweb tests, perl version is too old' :
+    test_done
+    exit
+}
+
 gitweb_init
 
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