[depends] Properly remove the native protobuf libraries

Summary: Depending on the architecture the installation can put libs in lib/, lib32/ or lib64/. Make sure to remove them all in the postprocessing step.

Test Plan: Run the gitian builds.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15469