changing exec to always use abs path

lib.go

@@ -235,7 +235,9 @@ func Exec(str string, opts ...*Opts) ([]*exec.Cmd, error) {
 	}
 
 	cmdwd := opt.Wd
-
+	if !filepath.IsAbs(cmdwd) {
+		cmdwd = filepath.Join(wd, cmdwd)
+	}
 	prepCmd := func(l Line) *exec.Cmd {
 		cmd := exec.Command(l.Tokens[0], l.Tokens[1:]...)
 		cmd.Stdout = log.Writer()