Rollup merge of #37667 - alexcrichton:fix-llvm-version, r=japaric

rustc_llvm: Require 3.9 for --link-static

Apparently stock Ubuntu 16.04 includes LLVM 3.8 which doesn't have this flag.

Author: eddyb

Diff for: src/librustc_llvm/build.rs

@@ -136,7 +136,7 @@ fn main() {
     let mut parts = version_output.split('.');
     if let (Some(major), Some(minor)) = (parts.next().and_then(|s| s.parse::<u32>().ok()),
                                          parts.next().and_then(|s| s.parse::<u32>().ok())) {
-        if major > 3 || (major == 3 && minor >= 8) {
+        if major > 3 || (major == 3 && minor >= 9) {
             cmd.arg("--link-static");
         }
     }