fix: set bg proc attr in build tagged file

exec.go

@@ -359,18 +359,6 @@ func execHandle(bg bool) interp.ExecHandlerFunc {
 
 		var j *job
 		if bg {
-			var procAttr *syscall.SysProcAttr
-			if runtime.GOOS == "windows" {
-				procAttr = &syscall.SysProcAttr{
-					CreationFlags: syscall.CREATE_NEW_PROCESS_GROUP,
-				}
-			} else {
-				procAttr = &syscall.SysProcAttr{
-					Setpgid: true,
-				}
-			}
-			cmd.SysProcAttr = procAttr
-
 			j = jobs.getLatest()
 			j.setHandle(&cmd)
 			err = j.start()

execfile_unix.go

@@ -4,8 +4,13 @@ package main
 
 import (
 	"os"
+	"syscall"
 )
 
+var bgProcAttr *syscall.SysProcAttr = &syscall.SysProcAttr{
+	Setpgid: true,
+}
+
 func findExecutable(path string, inPath, dirs bool) error {
 	f, err := os.Stat(path)
 	if err != nil {

execfile_windows.go

@@ -5,8 +5,13 @@ package main
 import (
 	"path/filepath"
 	"os"
+	"syscall"
 )
 
+var bgProcAttr *syscall.SysProcAttr = &syscall.SysProcAttr{
+	CreationFlags: syscall.CREATE_NEW_PROCESS_GROUP,
+}
+
 func findExecutable(path string, inPath, dirs bool) error {
 	nameExt := filepath.Ext(path)
 	pathExts := filepath.SplitList(os.Getenv("PATHEXT"))

job.go

@@ -43,6 +43,7 @@ func (j *job) start() error {
 		}
 		j.setHandle(&cmd)
 	}
+	j.handle.SysProcAttr = bgProcAttr
 
 	if !j.once {
 		j.once = true