Test 9500 - unhelpful without Perl::CGI

This has probably been going on forever, and the only reason I noticed
is that I had a machine that doesn't have perl-CGI installed.

I'm talking about t9500-gitweb-standalone-no-errors.

Anyway, if you don't have that, the test fails at everything, and it
does so without any clues about _why_ it fails. I ended up figuring it
out by doing a "strace -f" to see what seems to be wrong.

Maybe that test could have some additional check for "is perl::CGI
installed at all" and at least give a useful error message rather than
just saying it failed?

                    Linus