[Enhancement] Setting preference "build.path"

[AceyT]

"build.path" options

Hi

I've made changes to arduino-cli.py so that I could set in my preferences the build path that I want for a project. It's useful if I want to share the binary, and I thought that maybe others could want this feature as well

I've followed how the otption sketchbook.path was formatted since it's a preference Here's the code

        build_path = get_setting('build.path')
        if build_path:
        	args += ["--pref", "build.path={}".format(build_path)]

However, as explained per the Arduino man page, the folder must be already created Also, it will put everything (preprocessed .cpp files, compiled .o, etc...) However, in case of rebuild, it is much faster.