[CI] Wrap build_depends.sh on ibd.sh into functions
Summary:
This abstracts their path from the callsite.
Depends on D6689.
Test Plan:
./contrib/teamcity/build-configurations.sh build-osx ./contrib/teamcity/build-configurations.sh build-ibd
Reviewers: #bitcoin_abc, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D6690