build: GCC-12 build improvements

Summary:

2 changes to better support building with GCC 12, which out of the box, is currently broken if you want to build using depends.

Backport of core#25436.

Test Plan: Run the Linux64 build

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17032