Give the cross-crate generic some work to do

tests/codegen/remap_path_prefix/auxiliary/xcrate-generic.rs

@@ -3,4 +3,6 @@
 
 #![crate_type = "lib"]
 
-pub fn foo<T>() {}
+pub fn foo<T: Default>() -> T {
+    T::default()
+}

tests/codegen/remap_path_prefix/xcrate-generic.rs

@@ -7,7 +7,7 @@
 extern crate xcrate_generic;
 
 pub fn foo() {
-    xcrate_generic::foo::<u32>();
+    println!("{}", xcrate_generic::foo::<u32>());
 }
 
 // Here we check that local debuginfo is mapped correctly.