Integrate LLVM at llvm/llvm-project@81c99c5404c1

Updates LLVM usage to match
[81c99c5404c1](https://github.com/llvm/llvm-project/commit/81c99c5404c1)

PiperOrigin-RevId: 408864401

SUBMODULE_VERSIONS.txt

diff --git a/SUBMODULE_VERSIONS.txt b/SUBMODULE_VERSIONS.txt
index 492caf7..724a9f8 100644
--- a/SUBMODULE_VERSIONS.txt
+++ b/SUBMODULE_VERSIONS.txt
@@ -4,7 +4,7 @@
 aa533abfd4232b01f9e57041d70114d5a77e6de0 third_party/googletest
 88b845dee001723c4a0db1fe5477de735b6d3bb0 third_party/liburing
 acd6f6f014c25e46363e718381e0b35205df2d83 third_party/libyaml
-f0d997c4723214f5bc098b0acd2e61f3215d4a49 third_party/llvm-project
+81c99c5404c1aa92eadb7fb93dbeaae7bfaa5195 third_party/llvm-project
 839b119938b493ca2dc51597d2c11fb081d24c9c third_party/mlir-hlo
 3f701faace7addc75d16dea8a6cd769fa5b3f260 third_party/musl
 4c7697dbe973ed01ae6fbec37d186ebd05982e1f third_party/pybind11

third_party/llvm-project

diff --git a/third_party/llvm-project b/third_party/llvm-project
index f0d997c..81c99c5 160000
--- a/third_party/llvm-project
+++ b/third_party/llvm-project
@@ -1 +1 @@
-Subproject commit f0d997c4723214f5bc098b0acd2e61f3215d4a49
+Subproject commit 81c99c5404c1aa92eadb7fb93dbeaae7bfaa5195