aarch64-pointer-auth test failing on LLVM 19

[durin42]

Our CI has noticed that llvm/llvm-project@e15d67c broke tests/assembly/aarch64-pointer-auth.rs:

/var/lib/buildkite-agent/builds/rust-llvm-integrate/llvm-project/rust-llvm-integrate-prototype/tests/assembly/aarch64-pointer-auth.rs:16:11: error: CHECK: expected string not found in input
  | // CHECK: hint #25
  | ^
  | /var/lib/buildkite-agent/builds/rust-llvm-integrate/llvm-project/rust-llvm-integrate-prototype/build/x86_64-unknown-linux-gnu/test/assembly/aarch64-pointer-auth/aarch64-pointer-auth.s:1:1: note: scanning from here
  | .text
  | ^
  | /var/lib/buildkite-agent/builds/rust-llvm-integrate/llvm-project/rust-llvm-integrate-prototype/build/x86_64-unknown-linux-gnu/test/assembly/aarch64-pointer-auth/aarch64-pointer-auth.s:14:18: note: possible intended match here
  | .file "aarch64_pointer_auth.ed114bba7a018068-cgu.0"
  | ^
  |  
  | Input file: /var/lib/buildkite-agent/builds/rust-llvm-integrate/llvm-project/rust-llvm-integrate-prototype/build/x86_64-unknown-linux-gnu/test/assembly/aarch64-pointer-auth/aarch64-pointer-auth.s
  | Check file: /var/lib/buildkite-agent/builds/rust-llvm-integrate/llvm-project/rust-llvm-integrate-prototype/tests/assembly/aarch64-pointer-auth.rs

The only diff in the .s file is this:

--- working	2024-07-16 16:26:17.914057368 -0400
+++ broken	2024-07-16 15:35:19.788461411 -0400
@@ -18,11 +18,7 @@
 	.type	test,@function
 test:
 	.cfi_startproc
-	hint	#25
-	.cfi_negate_ra_state
 	mov	w0, #42
-	hint	#29
-	.cfi_negate_ra_state
 	ret
 .Lfunc_end0:
 	.size	test, .Lfunc_end0-test

So somehow something is causing the hint instructions to get dropped, which is the only thing the test actually looks for. I'm short on time today, but at least wanted to report this semi-promptly. I may look more soon.

[nikic]

We now need to also generate function attributes for this, instead of only the module metadata.