Fix frequent fail of non-clean builds
Fix frequent fail of non-clean builds

The build script was only emitting the rustc flags if it had to
regenerate config.rs. This is wrong, as it meant that builds that don't
regenerate config.rs lost the linker flags.

beatgammit/rust-lua,kballard/rust-lua,green-panther/rust-lua,tempbottle/rust-lua,beatgammit/rust-lua,green-panther/rust-lua,kballard/rust-lua,tempbottle/rust-lua