As mentioned in tock/tock#1666, binaries built with Rust are not reproducible by default. One main reason is panic messages that embed an absolute path to the file containing them (so building with --panic-console isn't reproducible by default).

We should apply the same techniques as in tock/tock#1666 to make OpenSK builds reproducible.

This would avoid issues like spurious linker errors when using a long build path, as discovered in #67.