TT#23286 Use /tmp instead of tmpfs as build directory for metapackages-piuparts

metapackages pulls in tons of packages and we run out of space
in tmpfs, so let's try executing it on disk instead.

Change-Id: Id55cd7f20c3535c044712f2d74df1fad01b1b79c

wrapper/piuparts_runner

@@ -18,6 +18,16 @@ rm -f piuparts.tap
 [ -n "${architecture:-}" ]     || architecture="$(dpkg --print-architecture)"
 [ -n "${mirror:-}" ]           || mirror='http://debian.sipwise.com/debian'
 
+if [ -n "${PROJECTNAME:-}" ] ; then
+  case "${PROJECTNAME}" in
+    metapackages)
+      echo "PROJECTNAME matches metapackages, using /tmp for the piuparts run instead of the tmpfs"
+      [ -n "${PIUPARTS_BASEDIR:-}" ] || PIUPARTS_BASEDIR="$(sudo mktemp --dry-run -d --tmpdir=/tmp/ --suffix=_piuparts_basetmp)"
+      [ -n "${PIUPARTS_TMPDIR:-}" ]  || PIUPARTS_TMPDIR="$(sudo mktemp -d --tmpdir=/tmp/ --suffix=_piuparts_tmp)"
+      ;;
+  esac
+fi
+
 echo "*** Executing $0 ***"
 echo "*** Using $PIUPARTS_BASEDIR as \$PIUPARTS_BASEDIR ***"
 echo "*** Using $PIUPARTS_TMPDIR as \$PIUPARTS_TMPDIR ***"