Add t/porting/utils.t, to test that utility scripts still compile.

Add t/porting/utils.t, to test that utility scripts still compile.

Right now, without this, it's possible to pass the all the regression tests
even if one has introduced syntax errors into scripts such as installperl
or installman. No tests fail, so it's fair game to push the commit.
Obviously this breaks installing perl, but we won't spot this.

Whilst we can't easily test that the various scripts *work*, we can at least
check that we've not made any trivial screw ups.