Integrate LLVM at llvm/llvm-project@21830c913505 (#1938)

diff --git a/WORKSPACE.bazel b/WORKSPACE.bazel
index 0029790..5a59ec7 100644
--- a/WORKSPACE.bazel
+++ b/WORKSPACE.bazel
@@ -28,9 +28,9 @@
     ],
 )
 
-LLVM_COMMIT = "3a82a1c3f6bdc9259cc4641f66fc76d1e171e382"
+LLVM_COMMIT = "21830c913505b1fd2cf10e454253483180c7e10b"
 
-LLVM_SHA256 = "c525cdb14bb239695852d696bcd13a6d47e579be18386ba2048515fe7f059153"
+LLVM_SHA256 = "1c79641c844278b10e2b5b5b9c4b72ab87a184a9689e36d3689208c67366da3a"
 
 http_archive(
     name = "llvm-raw",
diff --git a/build_tools/llvm_version.txt b/build_tools/llvm_version.txt
index 9bcc251..e3165a9 100644
--- a/build_tools/llvm_version.txt
+++ b/build_tools/llvm_version.txt
@@ -1 +1 @@
-3a82a1c3f6bdc9259cc4641f66fc76d1e171e382
+21830c913505b1fd2cf10e454253483180c7e10b