Add NXT support for GNU/Linux

[zhitm]

What?

I've added NXT support for GNU/Linux so this PR allows to compile and load programs via USB connection on Lego NXT.

Why?

Where's no NXT support for GNU/Linux, but it exist for Windows.

How?

I've changed structure of nxt-tools. There is no more division into win and linux directories. I use gcc-arm-none-eabi to compile C code on Linux same as on Windows. In order not to increase the volume of the installer, the user is given the opportunity to run the download-arm-none-eabi.sh script. There are some changes in compile.sh and compile.bat to pass sysroot as argument and use sysroot as compile option. There are also added more setting to choose cross compiler path as shown on image below. I've added widget dirPicker to choose path.

Screenshots

Other info

The imagePicker widget exist, but it only allows you to select image path. To reduce code repetitions it would be a good idea to unify that widget and dirPicker.

Linked pull requests

PR to nxt-tools PR to trik-help