Commit 235b523d ("meson: Use find_program() to resolve the
entitlement.sh script") didn't correctly fixed the issue, as
the script is still resolved for each target. Move the check
earlier, before processing each target.

Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Tested-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>