Make SANITIZER_MIN_OSX_VERSION a cache variable (#74394)

It is desirable to be able to configure the `-mmacosx-version-min` flag
for the sanitizers, but this flag was never made a CACHE variable in
cmake.

By doing this, it will allow developers to select different minimum
versions, which results in different interceptors being enabled or
disabled on their platforms. This version can now persist between cmake
runs, so it can be remembered by cmake, and edited in the cache file.