libvpx: universal build fails

[devernay (Frédéric Devernay)]

(seen with a ppc/i386 build on Leopard, I don't know if other universal builds fail the same way).

libvpx/Portfile uses muniversal, but the package uses a custom configure script which doesn't recognize the --host=... argument. Consequently, merger_host should be set to "" for all archs. Portfile should have

foreach my_arch ${configure.universal_archs} {

set merger_host(${my_arch}) ""

set merger_configure_args(${my_arch}) --target=$my_targets(${my_arch})-${os.platform}${os.major}-gcc

}

instead of

foreach my_arch ${configure.universal_archs} {

set merger_configure_args(${my_arch}) --target=$my_targets(${my_arch})-${os.platform}${os.major}-gcc

}