Add simple test for incremental compilation of delegations

Author: aerooneqq

tests/incremental/delegation-ice-155729.rs

@@ -0,0 +1,14 @@
+//@ revisions: bpass
+
+#![feature(fn_delegation)]
+
+pub mod to_reuse {
+    pub fn bar() {}
+}
+
+mod a {
+    use to_reuse;
+    reuse to_reuse::bar;
+}
+
+fn main() {}