release: require macOS 10.10+

Summary:
Qt 5.9.6 is incompatible with macOS < 10.10

Backport of core PR13617
https://github.com/bitcoin/bitcoin/pull/13617/files

Depends on D3912, D3913 and D3917.

Test Plan:
Run a native build with autotools and cmake.
Cross build with autotools and cmake.
Run the gitian build.

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D3919