Allow specifying msvc manifest file to use

[roblabla]

Hello, I'd like to integrate this tool in my nix-based msvc toolchain, replacing vsdownload.py from msvc-wine. But in order to do this, I need to ensure I can reproducibly download the source files from Microsoft.

To do so, vsdownload.py provides the ability to specify a manifest file, which is then used as-is instead of fetching the file from microsoft. See this. Downloading files from this pinned manifest is fully reproducible, as it pins the hash of all its sub-resources.

Having a similar ability in xwin would be great.

[Jake-Shadle]

Makes sense!

[K900]

Yes please! This would be very nice for CI builds as well.

[K900]

So as it turns out, there's still a reproducibility issue somewhere. On one machine, I get result/sdk/include/shared/ndis/{status.h,version.h}, and on the other machine the same files end up in result/sdk/include/um/alljoyn_c instead. That sounds like a threading/rayon issue, and I'm currently trying to rebuild with RAYON_NUM_THREADS=1.

[K900]

Actually, it looks like it might be this: https://github.com/Jake-Shadle/xwin/blob/main/src/splat.rs#L317

[K900]

Removing that check seems to make the output reproducible, or at least a lot more reproducible: K900@b1de334

[Jake-Shadle]

Ahh ok, that's unfortunate, if every SDK header is written then the output will contain a lot of duplicates, so I'll need to change this to filter out those duplicates in a deterministic manner.

[K900]

I tried switching it to use a BTreeMap and that seems to work, but only in single thread.