[CI] Move the environment variables to the configuration object
[CI] Move the environment variables to the configuration object

Summary:
The base environment variable are not dependent of the build context, so
move them to a more appropriated place.

Test Plan: Run any CI build.

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D7392

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