Make gitea work using cmd.exe again

Gitea will attempt to lookup its location using LookPath however,
this fails on cmd.exe if gitea is in the current working directory.

exec.LookPath will return an exec.ErrDot error which we can test for
and then simply using filepath.Abs(os.Args[0]) to absolute gitea
against the current working directory.

Fix go-gitea#22063

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/setting/setting.go

@@ -6,6 +6,7 @@ package setting
 
 import (
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"math"
 	"net"
@@ -465,6 +466,12 @@ func getAppPath() (string, error) {
 		appPath, err = exec.LookPath(os.Args[0])
 	}
 
+	if err != nil {
+		if !errors.Is(err, exec.ErrDot) {
+			return "", err
+		}
+		appPath, err = filepath.Abs(os.Args[0])
+	}
 	if err != nil {
 		return "", err
 	}