File call-flatpak-builder of Package build

#!/bin/bash

export BUILD_DIR=${BUILD_DIR:-/usr/lib/build}

IS_UNSHARED=

while test -n "$1" ; do
    case "$1" in
	--root)
	    BUILD_ROOT="$2"
	    shift 2
	    ;;
	--isunshared)
	    IS_UNSHARED=true
	    shift
	    ;;
	*)
	    break
	    ;;
    esac
done

if test -z "$BUILD_ROOT" ; then
    echo "Usage: call-flatpak-builder --root <buildroot>"
    exit 1
fi

if test -z "$IS_UNSHARED" ; then
    echo "Unsharing environment"
    # unshare mounts and network
    exec unshare -m -n $BUILD_DIR/call-flatpak-builder --isunshared --root "$BUILD_ROOT" "$@"
    exit 1
fi

if test -n "$IS_UNSHARED" ; then
    # make mounts private
    mount --make-rprivate /
fi

if test "$BUILD_ROOT" != '/' ; then
    # make build root a mount point
    mount --rbind --make-private "$BUILD_ROOT" "$BUILD_ROOT"
    mount --make-rprivate "$BUILD_ROOT"
fi

# setup mounts
test -e "$BUILD_ROOT/proc/self" || mount -n -tproc none $BUILD_ROOT/proc

set -x

# Build into repo
chroot "$BUILD_ROOT" bash -c "cd /usr/src/packages/FLATPAK_ROOT && flatpak-builder --default-branch=$FLATPAK_APP_VERSION --force-clean --repo=$FLATPAK_REPO build-dir $FLATPAK_FILE"

# Create bundle from repo
VERSION_RELEASE="$FLATPAK_APP_VERSION"
if [[ -n $RELEASE ]]; then
    VERSION_RELEASE+="-$RELEASE"
fi
chroot "$BUILD_ROOT" bash -c "flatpak build-bundle --runtime-repo=$FLATPAK_REMOTE $FLATPAK_REPO $TOPDIR/OTHER/$FLATPAK_APP-$VERSION_RELEASE.flatpak $FLATPAK_APP $FLATPAK_APP_VERSION"