scripts/nsis.py: Run dependency check for each DLL file only once

scripts/nsis.py: Run dependency check for each DLL file only once

Each DLL should only be checked once for dependencies, but
several hundred (781 in my test) unneeded checks were done.

Now the script is significantly faster (16 s in my build).

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20250111215244.1680931-1-sw@weilnetz.de>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250116160306.1709518-38-alex.bennee@linaro.org>