Emit function attribute "coroutine.presplit" for coroutines

This fixes issues with recent LLVM revisions that require this
attribute: https://llvm.org/docs/Coroutines.html.

Context:
cl/419786634
https://github.com/llvm/llvm-project/commit/c75cedc237f9747c5d5fe2a312d5ccc8531e2e70
https://reviews.llvm.org/D115790

Bug: b/165000222
Change-Id: I75308c6cf75d7aa9b823e7ded37f3f6ddf0a7010
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/61148
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

src/Reactor/LLVMReactor.cpp

diff --git a/src/Reactor/LLVMReactor.cpp b/src/Reactor/LLVMReactor.cpp
index fcd018a..a0d85c6 100644
--- a/src/Reactor/LLVMReactor.cpp
+++ b/src/Reactor/LLVMReactor.cpp
@@ -4318,6 +4318,7 @@
 	auto promisePtrTy = promiseTy->getPointerTo();
 
 	jit->function = rr::createFunction("coroutine_begin", handleTy, T(Params));
+	jit->function->addFnAttr("coroutine.presplit", "0");
 	jit->coroutine.await = rr::createFunction("coroutine_await", boolTy, { handleTy, promisePtrTy });
 	jit->coroutine.destroy = rr::createFunction("coroutine_destroy", voidTy, { handleTy });
 	jit->coroutine.yieldType = promiseTy;