Update LLVM to fix crash on Emscripten targets

Pulls in a bug fix from upstream to resolve #66308. Also adds a small
Rust regression test.

r? @alexcrichton

Author: tlively

src/llvm-project

@@ -0,0 +1,8 @@
+// build-pass
+// compile-flags: --crate-type lib
+
+// Regression test for LLVM crash affecting Emscripten targets
+
+pub fn foo() {
+    (0..0).rev().next();
+}