Integrate LLVM at llvm/llvm-project@668aa531d646

Updates LLVM usage to match
[668aa531d646](https://github.com/llvm/llvm-project/commit/668aa531d646)

PiperOrigin-RevId: 387732203

SUBMODULE_VERSIONS.txt

diff --git a/SUBMODULE_VERSIONS.txt b/SUBMODULE_VERSIONS.txt
index 47dfaa1..4ec0685 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
-6a7a2ee8161da84d9a58a88b497b0b47c8df99f3 third_party/llvm-project
+668aa531d646dfb0eff746f4b6e627cfb6a7a271 third_party/llvm-project
 be5715be382c6955aba0533a6dd5e50d79734bd0 third_party/mlir-hlo
 4c7697dbe973ed01ae6fbec37d186ebd05982e1f third_party/pybind11
 2e1b5fb39ebc2ef4cb77005f8267e4f3a6241ba1 third_party/spirv_cross

third_party/llvm-project

diff --git a/third_party/llvm-project b/third_party/llvm-project
index 6a7a2ee..668aa53 160000
--- a/third_party/llvm-project
+++ b/third_party/llvm-project
@@ -1 +1 @@
-Subproject commit 6a7a2ee8161da84d9a58a88b497b0b47c8df99f3
+Subproject commit 668aa531d646dfb0eff746f4b6e627cfb6a7a271