tectonic_cfg_support (cargo): A build.rs support crate that helps deal with CARGO_CFG_TARGET_* variables. When cross-compiling, these variables must be used instead of constructs such as `cfg!(target_arch = ...)` because the build.rs script is compiled to target the build host environment, not the true target environment. 
Keywords: rust|tex|tex-engine|tex-typesetting|texlive|typesetting|xetex