Add compile time feature compatibility check, remove from build.rs

build.rs

@@ -1,7 +0,0 @@
-fn main() {
-    // Must enable rcon on Windows
-    #[cfg(all(windows, not(feature = "rcon")))]
-    {
-        println!("cargo:warning=lazymc: you must enable rcon feature on Windows");
-    }
-}

src/main.rs

@@ -31,6 +31,10 @@ use std::env;
 
 use clap::App;
 
+// Compile time feature compatability check.
+#[cfg(all(windows, not(feature = "rcon")))]
+compile_error!("Must enable \"rcon\" feature on Windows.");
+
 /// Default log level if none is set.
 const LOG_DEFAULT: &str = "info";