Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tests/ui/enum_match_without_wildcard.rs

@@ -0,0 +1,16 @@
+#[cxx::bridge]
+mod ffi {
+    enum A {
+        FieldA,
+        FieldB,
+    }
+}
+
+fn main() {}
+
+fn matcher(a: ffi::A) -> u32 {
+    match a {
+        ffi::A::FieldA => 2020,
+        ffi::A::FieldB => 2021,
+    }
+}