fix: cross-platform build for SysProcAttr (#11)

Move syscall.SysProcAttr{Setpgid: true} behind build tags so the
binary compiles on Windows where Setpgid does not exist.

Author: nictuku

cmd/dynamic.go

@@ -7,7 +7,6 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
-	"syscall"
 	"time"
 
 	"github.com/pipeboard-co/pipeboard-cli/internal/client"
@@ -69,7 +68,7 @@ func maybeAutoRefresh(cache *ToolsCache) {
 	}
 	cmd := exec.Command(self, "refresh", "--if-changed")
 	cmd.Env = append(os.Environ(), "PIPEBOARD_AUTO_REFRESH=1")
-	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	setSysProcAttr(cmd)
 	cmd.Stdout = nil
 	cmd.Stderr = nil
 	_ = cmd.Start()

cmd/proc_unix.go

@@ -0,0 +1,14 @@
+//go:build !windows
+
+package cmd
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+// setSysProcAttr detaches the subprocess into its own process group
+// so it survives after the parent exits.
+func setSysProcAttr(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+}

cmd/proc_windows.go

@@ -0,0 +1,9 @@
+//go:build windows
+
+package cmd
+
+import "os/exec"
+
+// setSysProcAttr is a no-op on Windows; the subprocess runs independently
+// by default when stdout/stderr are nil.
+func setSysProcAttr(cmd *exec.Cmd) {}