Only pass -fno-use-linker-plugin on Windows

Only pass -fno-use-linker-plugin on Windows where it avoids pulling in
dependencies. Passing it to clang on OS X and Linux would make it fail
though.

Author: skade

src/librustc/back/link.rs

@@ -931,7 +931,12 @@ fn link_args(cmd: &mut Command,
     }
 
     // Rust does its' own LTO
-    cmd.arg("-fno-lto").arg("-fno-use-linker-plugin");
+    cmd.arg("-fno-lto");
+
+    // clang fails hard if -fno-use-linker-plugin is passed
+    if sess.targ_cfg.os == abi::OsWindows {
+        cmd.arg("-fno-use-linker-plugin");
+    }
 
     // If we're building a dylib, we don't use --gc-sections because LLVM has
     // already done the best it can do, and we also don't want to eliminate the