validation-test: Add regression test for #74609

Author: lexiippolito

validation-test/compiler_crashers_2_fixed/issue-74609.swift

@@ -0,0 +1,9 @@
+// RUN: %target-swift-frontend -target %target-swift-5.9-abi-triple -emit-ir %s
+
+struct Repeater<each Element> {
+  let elements: (repeat () -> each Element)
+}
+
+struct Box<T> {}
+
+let repeater: Repeater<Box<Int>>