Image build for reproducible output

To build an image (.hex) for a release requires a quality control of the build process. The image should be rebuilt as exactly as possible. Internal date based strings result in the image always being slightly different.

To build a release image, ensure out of platformio client, then delete all the local dependencies in eg for Documents\Arduino\env03\ModularSensors\examples\logging_to_EnviroDIY\logging_to_EnviroDIY.ino this is all the .piolibdeps & .pioenvs. All files should be committed to git especially in env03\ModularSensors\Src
Also ensure no files in temporary lib..

Start platformio - open folder env03\ModularSensors\examples\logging_to_EnviroDIY - press "build" icon.
This should pull in all dependent files defined in platformio.ini and build it.
The result is placed in env03\ModularSensors\examples\logging_to_EnviroDIY.pioenvs\mayfly\firmware.hex
Copy the image <.hex> to a release directory and filename

eg env03\release\mayfly_v0.19.2b.nh_190102_firmware.hex