Neo build on dev machines may find fmt from Homebrew, breaking build

Currently 7.2.5 fails to build on Mac OS due to the wrong path being utilised for fmt_DIR.

CMake defaults to the homebrew path (fmt_DIR:PATH=/opt/homebrew/lib/cmake/fmt) for fmt_DIR instead of utilising the path within the build directory (fmt_DIR:PATH=/Users/home/neo/build/tlm/deps/fmt.exploded/lib/cmake/fmt).

This issue seems to have been resolved in master, with the correct directory being set. We should backport the related patch.

Error:

couchbase/neo/build/tlm/deps/spdlog.exploded/include/spdlog/details/fmt_helper.h:57:9: error: no matching function for call to 'format_to'

Workaround:

Edit build/CMakeCache.txt, update fmt_DIR and build:

LIBEV_INCLUDE_DIR:PATH=<DIR TO COUCHBASE>/build/tlm/deps/fmt.exploded/lib/cmake/fmt

Other notes:

You may also run into the following:

error: no member named 'je_realloc' in namespace 'std'; did you mean simply 'je_realloc'?

Which will require the following patch to be cherry-picked for forestdb: https://review.couchbase.org/c/forestdb/+/208472