add sccache to build-test.yml

[altendky]

No description provided.

[coveralls-official]

Pull Request Test Coverage Report for Build 8135307016

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 85.2%

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Totals
Change from base Build 8115930322:	0.0%
Covered Lines:	11439
Relevant Lines:	13426

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💛 - Coveralls

[arvidn]

is this using some sccache service?
it would seem simpler (and perhaps more reliable) to use the github action cache action and point it to the cargo target directory (which essentially is a ccache already)

[arvidn]

Suggested change

	echo "SCCACHE_GHA_ENABLED=true" >> "$GITHUB_ENV"
	echo "SCCACHE_GHA_ENABLED=on" >> "$GITHUB_ENV"

according to: https://github.com/mozilla/sccache/blob/main/docs/GHA.md

[altendky]

https://github.com/mozilla-actions/sccache-action#conditionally-run-cache-and-enable-it says true which is where I copied it from. I haven't actually merged any PR using this though so we don't have any in-house precedence.

[altendky]

sccache has builtin GitHub Actions cache support. In my mind it can be way smarter than caching a directory this way. I hadn't dug into it but it might be able to be a global cache instead of per-repository with lots of duplication.