[llvm] fix template compilation issue in flang-rt, fix issue #160534 (PR #161250)

[Valentin Clement バレンタイン クレメン via llvm-commits]

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@@ -62,7 +62,7 @@ inline static RT_API_ATTRS void MatrixTransposedTimesMatrix(
     std::size_t yColumnByteStride = 0) {
   using ResultType = CppTypeFor<RCAT, RKIND>;
 
-  Fortran::runtime::memset(product, 0, rows * cols * sizeof *product);
+  std::memset(product, 0, rows * cols * sizeof *product);
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clementval wrote:

We cannot replace this because it might be unsupported. Look at `flang/include/flang/Runtime/freestanding-tools.h`

https://github.com/llvm/llvm-project/pull/161250