temporary builds of rust toolchain for qoriq (see https://github.com/SynoCommunity/spksrc/pull/5879)

The archive is built in toolchain/syno-qoriq-6.2.4/ with

tar -C work/rust/build/x86_64-unknown-linux-gnu/stage2 --exclude=src --exclude=rustc-src -cJf stage2_powerpc-unknown-linux-gnuspe.txz .