The build script currently panics with `opt-level=z` or `opt-level=s`. Account for this here.
Occasionally it is useful to see some information from running tests without making everything noisy from `--nocapture`. Add a function to log this kind of output to a file, and print the file as part of CI.
f16
f128
compiler-builtins
In preparation of adding routines from these two types, duplicate the `compiler-builtins` configuration here.