[flang] Merge pull request flang-compiler/f18#1068 from isuruf/strerror

Support platforms without strerror_r

Original-commit: flang-compiler/f18@85db30375c0c8095befeda6f4f2917d43002e4a4
Reviewed-on: https://github.com/flang-compiler/f18/pull/1068
tree: 0651c50c6bfaeaa0a3812372ddf1247e79a3ec7a
  1. flang/