d5ab20d23b
If the libstd-rs recipe is not correctly embedding LVM bitcode in its
output, then it can produce a toolchain that appears to work until you
try building a project that requests LTO:
error: failed to get bitcode from object file for LTO (Bitcode section not found in object file)
Enable LTO for rust-hello-world to give us an easy watch to catch such
problems.