Do not error on tz detection

In cases where systemd was not available, podman machine was erroring
out using timedatectl (it requires systemd).  on other providers like
windows, we don't do any timezone detection so it seems valid to return
a "" for timezone.  This fixes the first problem described #25950.

Fixes: https://github.com/containers/podman/issues/25950

Signed-off-by: Brent Baude <bbaude@redhat.com>

pkg/machine/ignition/ignition.go

@@ -151,7 +151,7 @@ func (ign *DynamicIgnition) GenerateIgnitionConfig() error {
 		if ign.TimeZone == "local" {
 			tz, err = getLocalTimeZone()
 			if err != nil {
-				return err
+				return fmt.Errorf("error getting local timezone: %q", err)
 			}
 		} else {
 			tz = ign.TimeZone

pkg/machine/ignition/ignition_linux.go

@@ -1,20 +1,29 @@
 package ignition
 
 import (
-	"errors"
 	"os"
 	"os/exec"
 	"strings"
+
+	"github.com/sirupsen/logrus"
 )
 
 func getLocalTimeZone() (string, error) {
+	trimTzFunc := func(s string) string {
+		return strings.TrimPrefix(strings.TrimSuffix(s, "\n"), "Timezone=")
+	}
+
+	// perform a variety of ways to see if we can determine the tz
 	output, err := exec.Command("timedatectl", "show", "--property=Timezone").Output()
-	if errors.Is(err, exec.ErrNotFound) {
-		output, err = os.ReadFile("/etc/timezone")
+	if err == nil {
+		return trimTzFunc(string(output)), nil
 	}
-	if err != nil {
-		return "", err
+	logrus.Debugf("Timedatectl show --property=Timezone failed: %s", err)
+	output, err = os.ReadFile("/etc/timezone")
+	if err == nil {
+		return trimTzFunc(string(output)), nil
 	}
-	// Remove prepended field and the newline
-	return strings.TrimPrefix(strings.TrimSuffix(string(output), "\n"), "Timezone="), nil
+	logrus.Debugf("unable to read /etc/timezone, falling back to empty timezone: %s", err)
+	// if we cannot determine the tz, return empty string
+	return "", nil
 }