fix: use golang.org/x/sys/execabs (#224)

Closes https://github.com/ooni/probe-engine/issues/1195

internal/cmd/jafar/iptables/iptables_integration_test.go

@@ -7,12 +7,13 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
-	"os/exec"
 	"runtime"
 	"strings"
 	"testing"
 	"time"
 
+	"golang.org/x/sys/execabs"
+
 	"github.com/apex/log"
 	"github.com/ooni/probe-cli/v3/internal/cmd/jafar/resolver"
 	"github.com/ooni/probe-cli/v3/internal/cmd/jafar/uncensored"
@@ -295,7 +296,7 @@ func TestHijackHTTP(t *testing.T) {
 	if err == nil {
 		t.Fatal("expected an error here")
 	}
-	var exitErr *exec.ExitError
+	var exitErr *execabs.ExitError
 	if !errors.As(err, &exitErr) {
 		t.Fatal("not the error type we expected")
 	}
@@ -335,7 +336,7 @@ func TestHijackHTTPS(t *testing.T) {
 		t.Fatal("expected an error here")
 	}
 	t.Log(err)
-	var exitErr *exec.ExitError
+	var exitErr *execabs.ExitError
 	if !errors.As(err, &exitErr) {
 		t.Fatal("not the error type we expected")
 	}

internal/cmd/jafar/main.go

@@ -10,11 +10,12 @@ import (
 	"net"
 	"net/http"
 	"os"
-	"os/exec"
 	"os/signal"
 	"strings"
 	"syscall"
 
+	"golang.org/x/sys/execabs"
+
 	"github.com/apex/log"
 	"github.com/apex/log/handlers/cli"
 	"github.com/miekg/dns"
@@ -243,7 +244,7 @@ func mustx(err error, message string, osExit func(int)) {
 	if err != nil {
 		var (
 			exitcode = 1
-			exiterr  *exec.ExitError
+			exiterr  *execabs.ExitError
 		)
 		if errors.As(err, &exiterr) {
 			exitcode = exiterr.ExitCode()