rust: allow /target and /debug to be symlinks

See rust-lang/cargo#4944 for the cargo change.

Rust.gitignore

@@ -1,7 +1,7 @@
 # Generated by Cargo
 # will have compiled files and executables
-debug/
-target/
+debug
+target
 
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html