[llvm] [llvm][Support] Add support for executing a detached process (PR #81708)

[Alexandre Ganea via llvm-commits]

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@@ -284,6 +285,8 @@ static bool Execute(ProcessInfo &PI, StringRef Program,
   unsigned CreateFlags = CREATE_UNICODE_ENVIRONMENT;
   if (AffinityMask)
     CreateFlags |= CREATE_SUSPENDED;
+  if (DetachProcess)
+    CreateFlags |= DETACHED_PROCESS;
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aganea wrote:

I don't know for Unix, but on Windows this flag prevents the I/O streams to be open on process startup, so any attempt to use `llvm::outs` or `llvm::errs` will most likely fail. Is that the intent?

https://github.com/llvm/llvm-project/pull/81708