fix: incompatible pointer type 'FARPROC'

error: assignment to 'BOOL (*)(DWORD)' {aka 'int (*)(long unsigned int)'} from incompatible pointer type 'FARPROC' {aka 'long long int (*)()'} [-Wincompatible-pointer-types]

src/gpgme-w32spawn.c

@@ -243,7 +243,7 @@ my_spawn (char **argv, struct spawn_fd_item_s *fd_list, unsigned int flags)
           handle = LoadLibrary ("user32.dll");
           if (handle)
             {
-              func = GetProcAddress (handle, "AllowSetForegroundWindow");
+              func = (BOOL (*)(DWORD)) GetProcAddress (handle, "AllowSetForegroundWindow");
               if (!func)
                 FreeLibrary (handle);
             }