testcommon: spawn-aware system() and qx[] workalikes

Barely noticeable on Linux, but this gives a 1-2% speedup
on a FreeBSD 11.3 VM and lets us use built-in redirects
rather than relying on /bin/sh.

1 files changed, 2 insertions, 1 deletions

diff --git a/t/nulsubject.t b/t/nulsubject.t
index b21507c2..1ded88d3 100644
--- a/t/nulsubject.t
+++ b/t/nulsubject.t
@@ -25,7 +25,8 @@ my $git_dir = "$tmpdir/a.git";
                 body => "hello world\n",
         ));
         $im->done;
-        is(system(qw(git --git-dir), $git_dir, 'fsck', '--strict'), 0, 'git fsck ok');
+        is(xsys(qw(git --git-dir), $git_dir, 'fsck', '--strict'), 0,
+                'git fsck ok');
 }
 
 done_testing();