[llvm] Revert "Remove dependence on <ciso646>" (PR #126399)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-support

Author: Jonas Devlieghere (JDevlieghere)

<details>
<summary>Changes</summary>

Reverts llvm/llvm-project#<!-- -->73273

---
Full diff: https://github.com/llvm/llvm-project/pull/126399.diff


1 Files Affected:

- (modified) llvm/include/llvm/Support/Threading.h (-1) 


``````````diff
diff --git a/llvm/include/llvm/Support/Threading.h b/llvm/include/llvm/Support/Threading.h
index 9972f4ad31dadb5..01e26ad9b858ea3 100644
--- a/llvm/include/llvm/Support/Threading.h
+++ b/llvm/include/llvm/Support/Threading.h
@@ -19,7 +19,6 @@
 #include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/Compiler.h"
 #include <optional>
-#include <version>
 
 #if defined(_MSC_VER)
 // MSVC's call_once implementation worked since VS 2015, which is the minimum

``````````

</details>


https://github.com/llvm/llvm-project/pull/126399