Add test for use of $crate in nested foreign macro_rules!

Author: Aaron1011

src/test/ui/hygiene/auxiliary/nested-dollar-crate.rs

@@ -0,0 +1,14 @@
+pub const IN_DEF_CRATE: &str = "In def crate!";
+
+macro_rules! make_it {
+    () => {
+        #[macro_export]
+        macro_rules! inner {
+            () => {
+                $crate::IN_DEF_CRATE
+            }
+        }
+    }
+}
+
+make_it!();

src/test/ui/hygiene/nested-dollar-crate.rs

@@ -0,0 +1,9 @@
+// aux-build:nested-dollar-crate.rs
+// edition:2018
+// run-pass
+
+extern crate nested_dollar_crate;
+
+fn main() {
+    assert_eq!(nested_dollar_crate::inner!(), "In def crate!");
+}