refactor: Include obj/build.h instead of build.h
Summary:
Partial backport of core PR11651 (commit 96b9281)
https://github.com/bitcoin/bitcoin/pull/11651/commits/96b92810a6a9719e03fe7004d5d5c2d6f7b7a5ff
Test Plan:
make check ninja check
Reviewers: #bitcoin_abc, deadalnix, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Subscribers: jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D2970