Allow generated source to be root module src.

rustfmt::skip breaks compilation when used as a root module source. We
don't run rustfmt on generated source anyhow.
See https://github.com/stepancheg/rust-protobuf/issues/493#issuecomment-652874447

Bug: 143953733
Test: rust_protobuf can generate library variants.
Change-Id: I0ea47de25c0ddd65781d6509b09ea648d11c4277
diff --git a/src/code_writer.rs b/src/code_writer.rs
index 8b53bc6..855b785 100644
--- a/src/code_writer.rs
+++ b/src/code_writer.rs
@@ -58,7 +58,8 @@
         self.write_line("#![allow(clippy::all)]");
         self.write_line("");
         self.write_line("#![allow(unused_attributes)]");
-        self.write_line("#![rustfmt::skip]");
+        // ANDROID CHANGE: comment out rustfmt::skip to fix compilation error.
+        //self.write_line("#![rustfmt::skip]");
         self.write_line("");
         self.write_line("#![allow(box_pointers)]");
         self.write_line("#![allow(dead_code)]");