Make the workspace hack local to RLS

.gitignore

@@ -2,3 +2,4 @@
 .idea
 
 target
+test_data/Cargo.lock

src/test/lens.rs

@@ -15,7 +15,6 @@ use crate::{
 };
 
 #[test]
-#[ignore] // FIXME(#925) intermittent failure
 fn test_lens_run() {
     let mut env = Environment::new("lens_run");
 

test_data/Cargo.toml

@@ -0,0 +1,5 @@
+# Make sure that test are not accidentally become members of
+# the main workspace in the rust-lang/rust repository
+[workspace]
+members = ["./*/"]
+exclude = ["./compiler_message", "./target"]