Fix problem with auth-source.el in Tramp

* lisp/net/tramp.el (tramp-read-passwd):
Use `tramp-compat-temporary-file-directory'.  (Bug#39389, Bug#39489)

Author: albinus

lisp/net/tramp.el

@@ -4849,7 +4849,12 @@ verbosity of 6."
   "Read a password from user (compat function).
 Consults the auth-source package.
 Invokes `password-read' if available, `read-passwd' else."
-  (let* ((case-fold-search t)
+  (let* (;; If `auth-sources' contains "~/.authinfo.gpg", and
+	 ;; `exec-path' contains a relative file name like ".", it
+	 ;; could happen that the "gpg" command is not found.  So we
+	 ;; adapt `default-directory'.  (Bug#39389, Bug#39489)
+	 (default-directory (tramp-compat-temporary-file-directory))
+	 (case-fold-search t)
 	 (key (tramp-make-tramp-file-name
 	       ;; In tramp-sh.el, we must use "password-vector" due to
 	       ;; multi-hop.