Move multi-file test to use auxiliary/ directory layout

Place submod.rs under tests/ui/attributes/auxiliary/ and use
#[path] to include it, matching the preferred compiletest
test structure. Removes the need for //@ ignore-auxiliary.

Author: Dnreikronos

tests/ui/attributes/auxiliary/submod.rs

@@ -0,0 +1 @@
+#![crate_name = "bar"]

…ile/crate-root-path-in-different-file.rs …tes/crate-root-path-in-different-file.rstests/ui/attributes/crate-root-path-in-different-file/crate-root-path-in-different-file.rs renamed to tests/ui/attributes/crate-root-path-in-different-file.rs tests/ui/attributes/crate-root-path-in-different-file/crate-root-path-in-different-file.rs renamed to tests/ui/attributes/crate-root-path-in-different-file.rs

@@ -1,5 +1,6 @@
 #![deny(unused_attributes)]
 
+#[path = "auxiliary/submod.rs"]
 mod submod;
 
 fn main() {}

…crate-root-path-in-different-file.stderr …crate-root-path-in-different-file.stderrtests/ui/attributes/crate-root-path-in-different-file/crate-root-path-in-different-file.stderr renamed to tests/ui/attributes/crate-root-path-in-different-file.stderr tests/ui/attributes/crate-root-path-in-different-file/crate-root-path-in-different-file.stderr renamed to tests/ui/attributes/crate-root-path-in-different-file.stderr

@@ -1,5 +1,5 @@
 error: the `#![crate_name]` attribute can only be used at the crate root
-  --> $DIR/submod.rs:2:1
+  --> $DIR/auxiliary/submod.rs:1:1
    |
 LL | #![crate_name = "bar"]
    | ^^^^^^^^^^^^^^^^^^^^^^