Various improvements in build script

[cmaglie]

This PR contains the following fixes:

• the IDE is now tolerant to missing package_index_bundled.json
• the IDE is now tolerant to missing bundled libraries folder or missing sketchbook/librarires
• the build script task arduino-builder-build has been factored out, so it's now more maintainable (one task for all architectures) and allow conditional build through env variable. This is based on @NicoHood's commit f29abf8

This should supersede and fix #5438

/cc @NicoHood

[ArduinoBot]

✅ Build completed.

Please test this code using one of the following:

⬇️ http://downloads.arduino.cc/javaide/pull_requests/arduino-PR-5778-BUILD-629-linux32.tar.xz
⬇️ http://downloads.arduino.cc/javaide/pull_requests/arduino-PR-5778-BUILD-629-linux64.tar.xz
⬇️ http://downloads.arduino.cc/javaide/pull_requests/arduino-PR-5778-BUILD-629-windows.zip
⬇️ http://downloads.arduino.cc/javaide/pull_requests/arduino-PR-5778-BUILD-629-macosx.zip
⬇️ http://downloads.arduino.cc/javaide/pull_requests/arduino-PR-5778-BUILD-629-linuxarm.tar.xz

ℹ️ The linuxarm build is still experimental and may not be always available.

[NicoHood]

Those commits are missing:
5de6c1f
4cee989

[NicoHood]

The IDE also should be tolerant of a missing tools-builder folder:
https://bugs.archlinux.org/task/52377

Any chance to see a better fix?

[cmaglie]

Those commits are missing:
5de6c1f
4cee989

Those are already cherry-picked in master branch:

d3bd5f2
1da9108
8e6422f

[cmaglie]

The IDE also should be tolerant of a missing tools-builder folder:
https://bugs.archlinux.org/task/52377

Any chance to see a better fix?

How can I reproduce that?
Maybe you should open another issue, to better track this bug.

[NicoHood]

you need to delete the described folder (or better move it somewhere else) and change platform.txt to point to the new loation. make sure your .arduino15 folder does not exist, otherwise the bug is not triggered (as it is not for me)

[cmaglie]

It seems the builder that requires (at least) one -tools option, can you open an issue on the builder repository?

[NicoHood]

Fixes seem to be applied properly. Thanks a lot!

The only thing left for packaging arduino securely now are the gpg signatures:
#5772 (comment)

You can use my gpgit script which is straight forward and super easy with github:
https://github.com/NicoHood/gpgit