dockerdeb: redirect 'cd' in export command to /dev/null

This had the unfortunate side effect of causing the environment to have a
newline due to the fact that some 'cd' outputs the result of the directory
change. So, let's just redirect the meaningless output.

contrib/dockerdeb

@@ -1,35 +1,35 b''
 #!/bin/bash -eu
 
 . $(dirname $0)/dockerlib.sh
 . $(dirname $0)/packagelib.sh
 
 BUILDDIR=$(dirname $0)
-export ROOTDIR=$(cd $BUILDDIR/..; pwd)
+export ROOTDIR=$(cd $BUILDDIR/.. > /dev/null; pwd)
 
 checkdocker
 
 DISTID="$1"
 CODENAME="$2"
 PLATFORM="$1-$2"
 shift # extra params are passed to build process
 
 OUTPUTDIR=${OUTPUTDIR:=$ROOTDIR/packages/$PLATFORM}
 
 initcontainer $PLATFORM
 
 # debuild only appears to be able to save built debs etc to .., so we
 # have to share the .. of the current directory with the docker
 # container and hope it's writable. Whee.
 dn=$(basename $PWD)
 
 if [ $(uname) = "Darwin" ] ; then
     $DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
             sh -c "cd /mnt/$dn && make clean && make local"
 fi
 $DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
   sh -c "cd /mnt/$dn && DEB_BUILD_OPTIONS='${DEB_BUILD_OPTIONS:=}' contrib/builddeb --build --distid $DISTID --codename $CODENAME"
 contrib/builddeb --cleanup --distid $DISTID --codename $CODENAME
 if [ $(uname) = "Darwin" ] ; then
     $DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
             sh -c "cd /mnt/$dn && make clean"
 fi