Makes buildroot bin scripts executable

buildroot/bin/build_marlin

buildroot/bin/generate_version_header_for_marlin

buildroot/bin/opt_disable

buildroot/bin/opt_enable

buildroot/bin/opt_enable_adv

buildroot/bin/opt_set

buildroot/bin/opt_set_adv

buildroot/bin/pins_set

buildroot/bin/restore_configs

buildroot/bin/use_example_configs