fix: ruby musl binaries in gem build

[sighphyre]

Number of small fixes to the build:

• Consumes the binary outputs from chore: publish musl binaries with correct names #160, related fixes to the way we're now loading the binaries in the Ruby code
• Moves the publish task to a one shot at the end of the build (timing meant this could sometimes fail for some gems)
• Removes the lock file, this is a library, the parent can resolve the gems. Importantly, this means we don't have to specify the platform we're building for, it'll be the platform the final program gets built for, which is important for musl builds