fix the crate name being used by the gencode library.

Before all invocations would try to create a library called protobuf_codegen_upb_gen_code. Now it should properly use the name of the crate currently being built.

PiperOrigin-RevId: 658414835

rust/protobuf_codegen/src/lib.rs

@@ -125,7 +125,7 @@ impl CodeGen {
                 }
             }
         }
-        cc_build.compile(&format!("{}_upb_gen_code", env!("CARGO_CRATE_NAME")));
+        cc_build.compile(&format!("{}_upb_gen_code", std::env::var("CARGO_PKG_NAME").unwrap()));
         Ok(())
     }