I just found that a new Arduino IDE release was rolled out last week with the Release Notes below:
ARDUINO 1.8.13 2020.06.16
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[arduino-builder]
* FIX REGRESSION: Fixed precompiled libraries containing "wrapper" code that has to be compiled together
with the precompiled part.
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After upgrading my Arduino IDE to v1.8.13, the BSEC Arduino library seems to be working as expected again!
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