contrib/buildrpm: force en_US locale during changelog's creation

Running this script using a different locale (i.e., Italian) returns
an error:
$ ./contrib/buildrpm
sto aggiornando la directory di lavoro
1060 file aggiornati, 0 file merge, 0 file rimossi, 0 file non risolti
errore: data errata in %changelog: mar giu 23 2009 Stefano Tortarolo <[e-mail]> 1.2.1-1034

contrib/buildrpm

@@ -1,72 +1,72 b''
 #!/bin/sh
 #
 # Build a Mercurial RPM in place.
 #
 # Bryan O'Sullivan <[e-mail]>
 #
 # Tested on
 # - Fedora 10
 # - Fedora 11
 # - Centos 5.3 (with Fedora EPEL repo for asciidoc)
 
 HG="`dirname $0`/../hg"
 PYTHONPATH="`dirname $0`/../mercurial/pure"
 export PYTHONPATH
 
 root="`$HG root 2>/dev/null`"
 specfile=contrib/mercurial.spec
 
 if [ -z "$root" ]; then
     echo 'You are not inside a Mercurial repository!' 1>&2
     exit 1
 fi
 
 rpmdir=/tmp/"`basename $root | sed 's/ /_/'`"-rpm # FIXME: Insecure /tmp handling
 
 cd "$root"
 rm -rf $rpmdir
 mkdir -p $rpmdir/RPMS
 $HG clone "$root" $rpmdir/BUILD
 
 if [ ! -f $specfile ]; then
     echo "Cannot find $specfile!" 1>&2
     exit 1
 fi
 
 tmpspec=/tmp/`basename "$specfile"`.$$ # FIXME: Insecure /tmp handling
 # Use the most recent tag as the version.
 version=`$HG tags | python -c 'import sys; print [l for l in sys.stdin.readlines() if l[0].isdigit()][0].split()[0]'`
 # Compute the release number as the difference in revision numbers
 # between the tip and the most recent tag.
 release=`$HG tags | python -c 'import sys; l = sys.stdin.readlines(); print int(l[0].split()[1].split(":")[0]) - int([x for x in l if x[0].isdigit()][0].split()[1].split(":")[0])'`
 tip=`$HG -q tip`
 
 # Beat up the spec file
 sed -e 's,^Source:.*,Source: /dev/null,' \
     -e "s,^Version:.*,Version: $version," \
     -e "s,^Release:.*,Release: $release," \
     -e "s,^%prep.*,Changeset: $tip\n\0," \
     -e 's,^%setup.*,,' \
     $specfile > $tmpspec
 
 cat <<EOF >> $tmpspec
 %changelog
-* `date +'%a %b %d %Y'` `$HG showconfig ui.username` $version-$release
+* `LANG=en_US date +'%a %b %d %Y'` `$HG showconfig ui.username` $version-$release
 - Automatically built via $0
 
 EOF
 $HG log \
      --template '* {date|rfc822date} {author}\n- {desc|firstline}\n\n' \
      .hgtags \
   | sed -e 's/^\(\* [MTWFS][a-z][a-z]\), \([0-3][0-9]\) \([A-Z][a-z][a-z]\) /\1 \3 \2 /' \
         -e '/^\* [MTWFS][a-z][a-z] /{s/ [012][0-9]:[0-9][0-9]:[0-9][0-9] [+-][0-9]\{4\}//}' \
    >> $tmpspec
 
 rpmbuild --define "_topdir $rpmdir" -bb $tmpspec
 if [ $? = 0 ]; then
     rm -rf $tmpspec $rpmdir/BUILD
     mv $rpmdir/RPMS/*/* $rpmdir && rm -r $rpmdir/RPMS
     echo
     echo "Packages are in $rpmdir:"
     ls -l $rpmdir/*.rpm
 fi