Add daita as a Cargo cfg variable

[Serock3]

Due to reasons outlined here #6202 (review), It may be problematic to gate DAITA behind a cargo feature. This is an alternative approach which avoids the use of features.

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This change is 

[MarkusPettersson98]

Reviewed 29 of 53 files at r1, 23 of 33 files at r3, 8 of 10 files at r4, 1 of 1 files at r5, all commit messages.
Reviewable status: 61 of 64 files reviewed, 3 unresolved discussions (waiting on @hulthe and @Serock3)

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build.sh line 168 at r3 (raw file):

if [[ "$(uname -s)" == "MINGW"* || "$(uname -s)" == "Linux" ]]; then
    CARGO_ARGS+=(--features daita)
fi

This should be removed, otherwise build.sh will fail when compiling due to the daita feature not existing on Linux and Windows 😊

Code quote:

# Enable DAITA on supported platforms
if [[ "$(uname -s)" == "MINGW"* || "$(uname -s)" == "Linux" ]]; then
    CARGO_ARGS+=(--features daita)
fi

[hulthe]

Reviewed 6 of 7 files at r2, 2 of 33 files at r3, all commit messages.
Reviewable status: 63 of 64 files reviewed, 3 unresolved discussions (waiting on @Serock3)

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.github/workflows/cargo-vendor.yml line 24 at r2 (raw file):

        run: |
          git config --global --add safe.directory '*'
          git submodule update --init --depth=1 dist-assets/binaries wireguard-go-rs/libwg

shouldn't this be wireguard-go-rs/libwg/wireguard-go?

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.github/workflows/desktop-e2e.yml line 164 at r5 (raw file):

        uses: actions/checkout@v2
      - name: Checkout submodules
       # TODO: should this specify a path? We don't want to pull `wireguard-go`

better to have it and not need it? 🤷
it's probably a non-issue to just keep this

[MarkusPettersson98]

Reviewed 1 of 5 files at r9.
Reviewable status: 61 of 78 files reviewed, 4 unresolved discussions (waiting on @dlon and @hulthe)

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.github/workflows/desktop-e2e.yml line 164 at r5 (raw file):

Previously, dlon (David Lönnhager) wrote…

+1

I agree

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.github/workflows/rust-unused-dependencies.yml line 92 at r7 (raw file):

Previously, dlon (David Lönnhager) wrote…

The macOS and Windows jobs can probably be merged if just the Install go step is skipped on Windows.

Done

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wireguard-go-rs/libwg/libwg.a line at r7 (raw file):

Previously, dlon (David Lönnhager) wrote…

This should probably be added to .gitignore? And completely removed from the git history as well (so it's not needlessly fetched).

Done (I think). Please verify that it is actually completely nuked from the git history 😊