cmUVProcessChain: Add Detached option for spawning daemons

Source/cmUVProcessChain.cxx

@@ -156,6 +156,12 @@ cmUVProcessChainBuilder& cmUVProcessChainBuilder::SetWorkingDirectory(
   return *this;
 }
 
+cmUVProcessChainBuilder& cmUVProcessChainBuilder::SetDetached()
+{
+  this->Detached = true;
+  return *this;
+}
+
 uv_loop_t* cmUVProcessChainBuilder::GetLoop() const
 {
   return this->Loop;
@@ -337,6 +343,9 @@ void cmUVProcessChain::InternalData::SpawnProcess(
   arguments.push_back(nullptr);
   options.args = const_cast<char**>(arguments.data());
   options.flags = UV_PROCESS_WINDOWS_HIDE;
+  if (this->Builder->Detached) {
+    options.flags |= UV_PROCESS_DETACHED;
+  }
 #if UV_VERSION_MAJOR > 1 ||                                                   \
   (UV_VERSION_MAJOR == 1 && UV_VERSION_MINOR >= 48) ||                        \
   !defined(CMAKE_USE_SYSTEM_LIBUV)
@@ -380,6 +389,9 @@ void cmUVProcessChain::InternalData::SpawnProcess(
          process.Process.spawn(*this->Loop, options, &process)) < 0) {
     process.Finish();
   }
+  if (this->Builder->Detached) {
+    uv_unref((uv_handle_t*)process.Process);
+  }
   process.InputPipe.reset();
   process.OutputPipe.reset();
 }

Source/cmUVProcessChain.h

@@ -39,6 +39,7 @@ public:
   cmUVProcessChainBuilder& SetExternalStream(Stream stdio, int fd);
   cmUVProcessChainBuilder& SetExternalStream(Stream stdio, FILE* stream);
   cmUVProcessChainBuilder& SetWorkingDirectory(std::string dir);
+  cmUVProcessChainBuilder& SetDetached();
 
   uv_loop_t* GetLoop() const;
 
@@ -69,6 +70,7 @@ private:
   std::vector<ProcessConfiguration> Processes;
   std::string WorkingDirectory;
   bool MergedBuiltinStreams = false;
+  bool Detached = false;
   uv_loop_t* Loop = nullptr;
 };