rustc: Stop relying on CFG_LIBDIR_RELATIVE

This is not sufficient for finding the library directory for binary
installs, but it does make the build more complex by requiring
env vars be set to build rustc.

src/librustc/metadata/filesearch.rs

@@ -235,8 +235,14 @@ pub fn rust_path() -> Vec<Path> {
 
 // The name of the directory rustc expects libraries to be located.
 // On Unix should be "lib", on windows "bin"
+#[cfg(unix)]
 pub fn libdir() -> ~str {
-    (env!("CFG_LIBDIR_RELATIVE")).to_owned()
+    ~"lib"
+}
+
+#[cfg(windows)]
+pub fn libdir() -> ~str {
+    ~"bin"
 }
 
 // The name of rustc's own place to organize libraries.