gdb: support daemonization on windows

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/google/shlex v0.0.0-20181106134648-c34317bd91bf
 	github.com/marcinbor85/gohex v0.0.0-20200531091804-343a4b548892
 	go.bug.st/serial v1.1.2
+	golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78
 	golang.org/x/tools v0.0.0-20200216192241-b320d3a0f5a2
 	tinygo.org/x/go-llvm v0.0.0-20210206225315-7fe719483a0f
 )

util_windows.go

@@ -4,10 +4,15 @@ package main
 
 import (
 	"os/exec"
+	"syscall"
+
+	"golang.org/x/sys/windows"
 )
 
 // setCommandAsDaemon makes sure this command does not receive signals sent to
-// the parent. It is unimplemented on Windows.
+// the parent.
 func setCommandAsDaemon(daemon *exec.Cmd) {
-	// Not implemented.
+	daemon.SysProcAttr = &syscall.SysProcAttr{
+		CreationFlags: windows.DETACHED_PROCESS,
+	}
 }