libpriv: Remove unnecessary builder causing memory leak

Remove the unnecessary builder causing memory leaks like this one:

Direct leak of 8 byte(s) in 1 object(s) allocated from:
    #0 0x7f60bd2fe3cf in __interceptor_malloc (/lib64/libasan.so.6+0xab3cf)
    coreos#1 0x7f60bca6cbb8 in g_malloc (/lib64/libglib-2.0.so.0+0x5bbb8)
    coreos#2 0x7f60bcaa54f2 in g_variant_type_copy (/lib64/libglib-2.0.so.0+0x944f2)
    coreos#3 0x7f60bcaa3384 in g_variant_builder_init (/lib64/libglib-2.0.so.0+0x92384)
    coreos#4 0x55e5bb3120d3 in filter_xattrs_cb src/libpriv/rpmostree-postprocess.cxx:1493
    coreos#5 0x7f60bc89cb38  (/lib64/libostree-1.so.1+0x49b38)
    coreos#6 0x7f60bc8a5e1a  (/lib64/libostree-1.so.1+0x52e1a)
    coreos#7 0x7f60bc8a622b in ostree_repo_write_dfd_to_mtree (/lib64/libostree-1.so.1+0x5322b)
    coreos#8 0x55e5bb307e6e in write_dfd_thread src/libpriv/rpmostree-postprocess.cxx:1551
    coreos#9 0x7f60bca92401  (/lib64/libglib-2.0.so.0+0x81401)
    coreos#10 0x7f60bc12d3f8 in start_thread (/lib64/libpthread.so.0+0x93f8)
    coreos#11 0x7f60bc05ab52 in __GI___clone (/lib64/libc.so.6+0x101b52)

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

src/libpriv/rpmostree-postprocess.cxx

@@ -1489,13 +1489,9 @@ filter_xattrs_cb (OstreeRepo     *repo,
 {
   g_assert (relpath);
 
-  GVariantBuilder builder;
-  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a(ayay)"));
-
   try {
     return filter_xattrs_impl(repo, relpath, file_info, user_data);
   } catch (std::exception& e) {
-      g_variant_builder_clear (&builder);
       /* Unfortunately we have no way to throw from this callback */
       g_printerr ("Failed to read xattrs of '%s': %s\n", relpath, e.what());
       exit (1);