Merge pull request #384 from dtolnay/minormax

If version detection fails, build with modernest stable features

Author: dtolnay

build.rs

@@ -43,14 +43,15 @@
 use std::env;
 use std::process::{self, Command};
 use std::str;
+use std::u32;
 
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
 
-    let version = match rustc_version() {
-        Some(version) => version,
-        None => return,
-    };
+    let version = rustc_version().unwrap_or(RustcVersion {
+        minor: u32::MAX,
+        nightly: false,
+    });
 
     if version.minor < 31 {
         eprintln!("Minimum supported rustc version is 1.31");