rustc: Move util::fs to rustc_back

Author: brson

src/librustc/lib.rs

@@ -125,11 +125,12 @@ pub mod plugin;
 pub mod lint;
 
 pub mod util {
+    pub use rustc_back::fs;
+
     pub mod common;
     pub mod ppaux;
     pub mod sha2;
     pub mod nodemap;
-    pub mod fs;
 }
 
 pub mod lib {

src/librustc/util/fs.rs renamed to src/librustc_back/fs.rs

@@ -45,6 +45,7 @@ extern crate flate;
 pub mod abi;
 pub mod archive;
 pub mod arm;
+pub mod fs;
 pub mod mips;
 pub mod mipsel;
 pub mod rpath;