Use execvp() instead of execvpe()

Nothing here changes environ directly, and we're not interested
in passing a specific custom environment to kwin_wayland, so
don't use the (Linux-only) execvpe() for passing environment.

helpers/wayland_wrapper/kwin_wrapper.c

@@ -59,7 +59,7 @@ pid_t launch_kwin(struct wl_socket *socket, int argc, char **argv)
 
         args[pos++] = NULL;
 
-        execvpe("kwin_wayland", args, environ);
+        execvp("kwin_wayland", args);
         free(args);
         exit(127); /* if exec fails */
     } else {