I have noticed that Linux x86_64 fastdebug build jobs started to fail in GHA with no free space left on device. Instrumenting GHA runs shows we have about 17G of free space on those runners:

Filesystem Size Used Avail Use% Mounted on
/dev/root 72G 56G 17G 78% /

My local x86_64 fastdebug build takes about 16G:

$ du -sh build/linux-x86_64-server-fastdebug/
16G build/linux-x86_64-server-fastdebug/

So we are very close to the limit, and no wonder we run over. While we can probably improve the build footprint to work better with this limit (e.g. JDK-8374508), we also want to see if we can do anything on GHA side to mitigate this.

GHA docs say there is 14G of guaranteed disk space on runners:
https://docs.github.com/en/actions/reference/runners/github-hosted-runners#standard-github-hosted-runners-for-public-repositories

...so we need to squeeze just a bit.