pkb/build: extractRootCause for NetBSD too
pkb/build: extractRootCause for NetBSD too

* pkg/build: share extractRootCause with openbsd

This should get kernel build errors reported in syz-ci console.

* Add a test

* lint

* pkb/build: extractRootCause for NetBSD too

google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller