v7.0.0-pr.3637.2

PR testing build for #3637 — provider-agnostic PostgreSQL (#3636, #3734, #3735, #3736).

Supersedes v7.0.0-pr.3637.1, whose migrator image build failed in its own self-check: the check ran ldconfig under qemu, which segfaults for exactly the reason the surrounding workaround exists. The build itself was already fixed in .1; .2 fixes the check.

Neither .0 nor .1 published any artifact.

Not for production use.