Don't use static crt by default when build proc-macro Don't check value of `crt-static` when build proc-macro crates, since they are always built dynamically. For more information, see https://github.com/rust-lang/cargo/issues/7563#issuecomment-591965320 I hope this will fix issues about compiling `proc_macro` crates on musl host without bring more issues. Fix https://github.com/rust-lang/cargo/issues/7563