WinARM Preliminary Support

[synopse]

Windows on 64-bit ARM is a fact, with existing nice hardware (mostly laptops) around.

Goal of this issue is to see how far we could use FPC trunk to compile natively to the aarch64-win64 plaform.
We have very good support of arch64-linux support since years, validated nightly using our Tranquil IT LUTI Ampere server. ;)

We have identified and already fixed (circumvented) some compiler issues.
This entry could be used to mark new work in this direction.

[synopse]

Some hints:

• The FPC trunk is required to have the aarch64-win64 target;
• The FPC trunk seems broken and require -O1 at most (not -O2 or -O3 due to incorrect register allocations) - on all platforms, not only aarch64-win64;
• There are still some issues but some part of mormot2tests do pass;
• Weirdly enough, the tests are slower in native aarch64 than with a x86_64-win64 executable running within PRISM emulation - and definitively more stable since all tests do pass with PRISM once the threads pressure is reduced;
• Tested today with git hash e9579fe2df.

Here are some tests

• with native arm64 compilation
• with Intel Win64 PRISM emulation