[flang] [llvm] [flang] Add runtime and lowering implementation for extended intrinsic PUTENV (PR #134412)

[Eugene Epshteyn via llvm-commits]

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@@ -45,6 +45,15 @@ struct ExecutionEnvironment {
   const char *GetEnv(
       const char *name, std::size_t name_length, const Terminator &terminator);
 
+  std::int32_t SetEnv(
+      const char *name, std::size_t name_length,
+      const char *value, std::size_t value_length,
+      const Terminator &terminator);
+
+  std::int32_t UnsetEnv(
+      const char *name, std::size_t name_length,
+      const Terminator &terminator);
+
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eugeneepshteyn wrote:

`SetEnv()` and `UnsetEnv()` could be used by the rest flang-rt, if necessary

https://github.com/llvm/llvm-project/pull/134412