Compile static versions of gcc libraries

Since default configure options for host packages include
--disable-static, gcc was not configured to build static version of its
libraries (libgcc.a, libstdc++.a, ...).

This patch replace --disable-static by --enable-static in configure
command. Notice some options was removed sinces they was ignored by gcc
configure script.

Once it was compiled, this commit takes care to copy static libraries to
$STAGING

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Tested-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>