This was introduced before `#[panic_handler]` was stable, but should no
longer be needed. Additionally, we only need it for
`builtins-test-intrinsics`, not as a dependency of `compiler-builtins`.
The current setup has the `Cargo.toml` for `compiler-builtins` at the
repository root, which means all support crates and other files are
located within the package root. This works for now but is not the
cleanest setup since files that should or shouldn't be included in the
package need to be configured in `Cargo.toml`. If we eventually merge
`libm` development into this repository, it would be nice to make this
separation more straightforward.
Begin cleaning things up by moving the crate source to a new
`compiler-builtins` directory and adding a virtual manifest. For now the
`libm` submodule is also moved, but in the future it can likely move
back to the top level (ideally `compiler-builtins/src` would contain a
symlink to `libm/src/math`, but unfortunately it seems like Cargo does
not like something about the submodule + symlink combination).
This is what `cc-rs` is using and should create a release PR whenever a
change to `master` is made. If the branch is merged, it should publish
the new version.
Includes configuration to disable semver checks and not keep a changelog
since this is an implementation detail.
