fa1cffacae ci: Install missing nproc in macos task (MarcoFalke)
faf7a2bccc ci: Add missing -DWERROR=ON to test-each-commit (MarcoFalke)
Pull request description:
Found by in Sjors in https://github.com/bitcoin/bitcoin/pull/27260#discussion_r1785860610 (Thanks!)
Also, includes an unrelated commit to simplify the ci scripts, by assuming nproc exists on macos as well. (Having more than one commit is also required to trigger the `test-each-commit` task)
ACKs for top commit:
theuni:
utACK fa1cffacae.
Tree-SHA512: 881df6964da31c3f7161b763bdf74029743567272c7a4db24ded10909a8cedad39b494a9f486f0b059bbeb0beb190dcd91369650d014e1fc3b5f7ae07cd54771