CI: Disable incremental build for faster CI

[oech3]

benchmark (closes #10459 ): 18m 28s -> 15m 40s
l10n: 28m 23s -> 16m 1s
CICD: 44m 52s -> 31m 35s
code-quality: 6m 53s -> 7m 26s (bad)

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.

[oech3]

@xtqqczze @ChrisDryden I'm not familiar with this. Would you check that am I missing something?

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)

[oech3]

?! 2nd result is gabadge.

[oech3]

I guess it was caused by traffic jam...? Faster than main now (i.e. main is slow

[xtqqczze]

@oech3 Are you definitely sure incremental compilation was enabled?

The dtolnay/rust-toolchain action that we use seems to be configured to disable it:

https://github.com/dtolnay/rust-toolchain/blob/f7ccc83f9ed1e5b9c81d8a67d7ad1a747e22a561/action.yml#L110

[oech3]

Hmm ... I think it reduced size of uploaded caches.

[oech3]

I might misunderstood by CIs using VM, rustup, or preinstalled rust .

[xtqqczze]

Well at least it doesn't hurt to be explicit about CARGO_INCREMENTAL.

[oech3]

Yes. It works if we decided to use preinstalled rust.

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Well at least it doesn't hurt to be explicit about CARGO_INCREMENTAL.