buildtools-extended-tarball: Add libstc++.a

Builds like native-openjdk, really wants a to link
some tools against the static version. Since when
using the extended tarball, its the only place to
get it, add the library.

Signed-off-by: Jeremy Puhlman <jpuhlman@mvista.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>