Rollup merge of #52439 - o01eg:fix-52317, r=alexcrichton

Revert some changes from #51917 to fix custom libdir

Should fix #52317 also adds `libdir` value to output.

src/bootstrap/builder.rs

@@ -825,7 +825,7 @@ impl<'a> Builder<'a> {
             cargo.env("RUSTC_ERROR_FORMAT", error_format);
         }
         if cmd != "build" && cmd != "check" && want_rustdoc {
-            cargo.env("RUSTDOC_LIBDIR", &libdir);
+            cargo.env("RUSTDOC_LIBDIR", self.sysroot_libdir(compiler, self.config.build));
         }
 
         if mode.is_tool() {