compiler.optimization_flags
allows for specifying the desired optimization level during compilation. by @aentinger in https://github.com/arduino/ArduinoCore-renesas/pull/238
Full Changelog: https://github.com/arduino/ArduinoCore-renesas/compare/1.0.5...1.1.0
Full Changelog: https://github.com/arduino/ArduinoCore-renesas/compare/1.0.4...1.0.5