Support thrift_library::rust_include_srcs

Summary:
`rust_include_srcs` is supported on `thrift_library` as a way of including other Rust code in the generated crate, generally used to implement other traits on the generated types.

Adding support for this in autocargo by copying these files into the output dir and making sure their option is specified to the thrift compiler

Reviewed By: ahornby

Differential Revision: D30789835

fbshipit-source-id: 325cb59fdf85324dccfff20a559802c11816769f

src/dep_tests/cargo_thrift/thrift_build.rs

@@ -32,6 +32,11 @@ fn main() {
             conf.options(options);
         }
 
+        let include_srcs = vec![
+
+        ];
+        conf.include_srcs(include_srcs);
+
         conf
     };