common/chroot-style: add unshare wrapper script

common/chroot-style/unshare.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+#
+# This chroot script uses unshare(1) with user_namespaces(7).
+#
+readonly MASTERDIR="$1"
+readonly DISTDIR="$2"
+readonly HOSTDIR="$3"
+readonly EXTRA_ARGS="$4"
+
+if ! command -v unshare >/dev/null 2>&1; then
+	exit 1
+fi
+
+if [ -z "$XBPS_IS_UNSHARED" ]; then
+	XBPS_IS_UNSHARED=1 exec unshare $EXTRA_ARGS -m -U -r -- "$0" "$@"
+	exit 1
+fi
+
+shift 4
+
+if [ -z "$MASTERDIR" -o -z "$DISTDIR" ]; then
+	echo "$0 MASTERDIR/DISTDIR not set"
+	exit 1
+fi
+
+for i in /dev /proc /sys; do
+	mount --rbind "$i" "$MASTERDIR/$i" || exit 1
+done
+mount --rbind "$DISTDIR" "$MASTERDIR/void-packages" || exit 1
+mount --rbind "$HOSTDIR" "$MASTERDIR/host" || exit 1
+exec chroot "$MASTERDIR" "$@"