tools: unify make-v8.sh for ppc64le and s390x

Refactor `tools/make-v8.sh` to minimise differences between the
`ppc64le` and `s390x` paths to allow us to enable `ccache` on the
`ppc64le` machines in the CI.

PR-URL: https://github.com/nodejs/node/pull/31628
Refs: https://github.com/nodejs/build/pull/1927
Refs: https://github.com/nodejs/build/issues/1940


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>