Finally switch to ARM GCC 9, new Cygwin, new Ant, new openJDK

[MaEtUgR]

• ARM GCC 9 is supported by the NuttX we use since https://github.com/PX4/Firmware/pull/15139 and the Windows build got fixed with https://github.com/PX4/Firmware/pull/16040 so I'm switching to ARM GCC 9 to use the toolchain on PX4 master
• Apache Ant always deletes the old version (URL no longer available) when a new one comes out so I'm updating the version
• For the Windows toolchain I hosted an old portable JDK version for a long time now. This is not really a security issue since the version does not get installed or is accessible through the PATH. It only resides in its folder and gets used to build jmavsim. Nevertheless it makes sense to update and since I discovered openJDK is providing portable zip archives which Oracle is not I'm switching.
• Also correct the SITL build target which changed a long time ago.

[hamishwillee]

@MaEtUgR No .msi file? (or on Amazon)? When that exists also need to update https://dev.px4.io/master/en/setup/dev_env_windows_cygwin.html

[MaEtUgR]

@hamishwillee Right, I tagged to make CI build a new installer but it failed. Then I debugged locally since the error message is unexpected and it's reproducable but still hard to find. Maybe it has something to do with the size or number of files. Not solved yet. I'll run CI again once I figured it out.

[hamishwillee]

Thanks @MaEtUgR . Been wondering when this would arrive :-)

[MaEtUgR]

I figured the main problem is file size. The files to compress into the installer archive exceed 2GB and that's not supported in WiX. So I need to either find a way to strip it down or split it up into multiple archives (which is tedious to download). I checked and the reason is Cygwin increasing its size of the base installation.