Add support for building 64-bit static Linux binary
It seemed easiest to include the linux binary in our existing reproducer, because we can re-use the entire infrastructure. A full run on our CI takes ~45min now though. The linux binary seems to be reproducible, as confirmed by Santiago.
Please review the linux build script carefully. It mimicks the Android one as close as possible, but I couldn't use the Makefile since it was NDK specific.