Build compiler_builtins by default? #212
Description
With rust-lang/rust#49503 the compiler_builtins crate is injected to no_std crates by default. Thus, a Xargo.toml that builds compiler_builtins is always required now (see rust-lang/rust#49503 (comment)). Would it make sense to update xargo default to build compiler_builtins even without a Xargo.toml?