Fix spurious compile error

From time to time, I would get this error:

[...]
sed: -e expression #8, char 41: Unterminated `s' command
make: *** [git-add--interactive] Error 1

Turns out that the function WriteMakefile() called in Makefile.PL
outputs the message "Writing perl.mak for Git" to stdout! Thus,
the output of "make -C perl -s --no-print-directory instlibdir"
would be prefixed by that message whenever Makefile.PL was newer
than perl.mak.

This is fixed by redirecting stdout to stderr in Makefile.PL.

Signed-off-by: Johannes E. Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

perl/Makefile.PL

@@ -20,6 +20,10 @@ if ($@) {
 my %extra;
 $extra{DESTDIR} = $ENV{DESTDIR} if $ENV{DESTDIR};
 
+# redirect stdout, otherwise the message "Writing perl.mak for Git"
+# disrupts the output for the target 'instlibdir'
+open STDOUT, ">&STDERR";
+
 WriteMakefile(
 	NAME            => 'Git',
 	VERSION_FROM    => 'Git.pm',