correa authored Jun 10, 2020 and Brad King committed Jun 11, 2020

When boost is built with `BZIP2_SOURCE` or `ZLIB_SOURCE` it will
generate boost versions of these libraries.  Since commit cb1a434c
(FindBoost: Add check headers for `zlib` and `bzip2`, 2016-07-01,
v3.7.0-rc1~400^2) we look for them only on Windows where they are
commonly provided, but they may be available on every platform.