RFR: 8294941: GHA: Cut down cross-compilation sysroots

[Christoph Langer]

On Fri, 7 Oct 2022 07:48:21 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> In GHA cross-compilation, we don't need everything from the sysroot, because we use native compilers for the compilation. Therefore, we can cut them even deeper and reclaim significant amount of cache space. This would also make cache eviction less likely, which saves time on recreating the sysroots when that happens.
> 
> Current sysroots take about 300M per arch, which quickly multiplies up for multiple arches (we build 5 now), users (ballparking at about 200 active contributors). This amounts to about 1500M caches per job, and 300G in caches across our org for a single JDK tree. Update releases also use GHA for their testing, but the number of contributors there is lower. Still, I think it slides to TB territory now.
> 
> In my local tests, new aarch64 sysroot tar.gz gets reduced from 315M to just 85M, about 3.7x improvement. Even deeper cuts are possible, but they would affect the redundant `.so`-s in `/usr/lib/${arch}/`. That would be much more fragile to do and might affect our builds. Therefore, I stopped at doing just these.

Looks good.

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Marked as reviewed by clanger (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10601