isync: add default SASL mechanisms when using cyrus-sasl-xoauth2

The XOAUTH2 support was added in 47eda8e, overriding `SASL_PATH` and
dropping all default SASL mechanisms from `cyrus_sasl`. The option was
disabled by default in fe02c5e, but users manually overriding isync to
enable `withCyrusSaslXoauth2` still face this issue.

This commit sets `SASL_PATH` to a combination of `cyrus_sasl` and
`cyrus-sasl-xoauth2`, as suggested in #235959.

pkgs/tools/networking/isync/default.nix

@@ -30,7 +30,7 @@ stdenv.mkDerivation rec {
 
   postInstall = lib.optionalString withCyrusSaslXoauth2 ''
     wrapProgram "$out/bin/mbsync" \
-        --prefix SASL_PATH : "${lib.makeSearchPath "lib/sasl2" [ cyrus-sasl-xoauth2 ]}"
+        --prefix SASL_PATH : "${lib.makeSearchPath "lib/sasl2" [ cyrus-sasl-xoauth2 cyrus_sasl.out ]}"
   '';
 
   meta = with lib; {