Since LLVM v15, llvm-objcopy seems to produce broken (misaligned?)
binaries, which when combined with some difficult to debug timing issues
caused by the calibrate_dac_feedback routine, would cause the
independent watchdog to kick in, and bootloop the Thermostat.
As NixOS 23.11 ships LLVM v16, upgrading to it breaks builds. Using
rust-objcopy from cargo-binutils does not help either since the pinned
version of Rust uses LLVM v15.
arm-none-eabi-objcopy doesn't have this problem, so use it instead.
See https://github.com/llvm/llvm-project/issues/58407 and
https://github.com/rust-lang/rust/issues/102983.
