tinydm-run-session: parse .desktop arrays correctly (MR 19)

Citing [1]:

$XDG_CURRENT_DESKTOP should have been set by the login manager,
according to the value of the DesktopNames found in the session file.
The entry in the session file has multiple values separated in the
usual way: with a semicolon.

[1]: https://specifications.freedesktop.org/desktop-entry-spec/latest/recognized-keys.html
Fixes: e7a35226

tinydm-run-session.sh

@@ -45,7 +45,7 @@ source_session_profiles() {
 # $1: file
 # $2: key
 parse_xdg_desktop() {
-	grep "^$2=" "$1" | cut -d "=" -f 2-
+	grep "^$2=" "$1" | cut -d "=" -f 2- | tr ';' ':' | sed 's/:$//'
 }
 
 # $1: Exec line from .desktop file