Draft: windows on arm lib support

[ahorek]

Related to #4697

Description of the Change
this allows compiling BOINC libraries with https://github.com/Windows-on-ARM-Experiments/mingw-woarm64-build/ for cross-compilation. Windows on ARM will officially be supported in the upcoming GCC 15.

Alternate Designs
Visual Studio is an alternative, it allows ARM targets, but it doesn't support cross-compilation, so using a GCC is more convenient because there's no need to access the real hardware.

while this change fixes the build
./configure --host="aarch64-windows" --with-boinc-platform="windows_aarch64" --disable-server --disable-manager --disable-client --disable-shared CXXFLAGS="-O3 "

I'm not sure what the platform string should be... ? https://boinc.berkeley.edu/trac/wiki/BoincPlatforms

I also have to run more tests to ensure it works with apps, so it's a draft for now, but any feedback is welcome. Thanks!

[AenBleidd]

Thank you for your PR.
I converted it to 'Draft' since the same is mentioned in your PR title, and will review it later.
Just for the reference, Visual Studio supports cross-compilation, you just need to install required components to it, and it already builds for ARM64 on our CI:

• https://github.com/BOINC/boinc/actions/runs/12100618832/job/33739454467
• https://github.com/BOINC/boinc/actions/runs/12100618832/job/33739454280

[AenBleidd]

Please also add one more CI flow to run ARM64 builds with mingw: https://github.com/BOINC/boinc/blob/master/.github/workflows/mingw.yml

[AenBleidd]

All these are not required since WSL is supported on ARM64 devices as well: https://learn.microsoft.com/en-us/windows/wsl/install-manual

[ahorek]

ok, I'm encountering a relocation error during linking... let's see if I can find a better solution

[AenBleidd]

is this really required?

[ahorek]

it's for size_t https://github.com/BOINC/boinc/blob/master/lib/boinc_win.h#L164C9-L164C15

[ahorek]

Thank you for your PR. I converted it to 'Draft' since the same is mentioned in your PR title, and will review it later. Just for the reference, Visual Studio supports cross-compilation, you just need to install required components to it, and it already builds for ARM64 on our CI:

* https://github.com/BOINC/boinc/actions/runs/12100618832/job/33739454467

* https://github.com/BOINC/boinc/actions/runs/12100618832/job/33739454280

ok. Even with an empty hello world project, I'm getting LNK1112: module machine type 'x86' conflicts with target machine type 'ARM' , and the binary isn't generated. I'll see if there's a way to fix it somehow. Thanks

[ahorek]

unfortunately, using https://github.com/Windows-on-ARM-Experiments/mingw-woarm64-build/ the app is crashing at boinc_init(). Without a backtrace or tools like gdb (which aren't available on Windows ARM), I probably won't be able to fix it.

It would be great to support GCC 15 for building Win+ARM once it becomes officially available. https://www.phoronix.com/news/GCC-aarch64-w64-mingw32 but this change doesn't seem to be sufficient.

[ahorek]

btw I successfully built and tested the app in Visual Studio after installing additional ARM SDK libraries.