invocation of readlink fails on macOS build

The macOS m1 task is failing on Evergreen as a result of the .evergreen/find-cmake.sh script in the C driver project (which is called by the libmongocrypt build) invoking the readlink command with an option not supported on macOS:

[2022/04/11 16:54:27.454] ++++ readlink -f cmake-install

[2022/04/11 16:54:27.454] readlink: illegal option -- f

[2022/04/11 16:54:27.454] usage: readlink [-n] [file ...]