xbps-src: correctly cleanup masterdir/tmp (really)

previous commit led to
```
rm: refusing to remove '.' or '..' directory: skipping 'void-packages/masterdir/tmp/.'
rm: refusing to remove '.' or '..' directory: skipping 'void-packages/masterdir/tmp/..'
```

xbps-src

@@ -737,8 +737,9 @@ case "$XBPS_TARGET" in
             [ -d "$XBPS_BUILDDIR" ] && chmod -R +wX $XBPS_BUILDDIR
             rm -rf \
                 $XBPS_BUILDDIR \
-                $XBPS_DESTDIR \
-                $XBPS_MASTERDIR/tmp/* $XBPS_MASTERDIR/tmp/.*
+                $XBPS_DESTDIR
+            rm -rf $XBPS_MASTERDIR/tmp
+            mkdir -p $XBPS_MASTERDIR/tmp
         else
             read_pkg
             if [ -n "$CHROOT_READY" -a -z "$IN_CHROOT" ]; then