Platforms other than Linux don't benefit from our Valgrind evergreen tasks. We can consider making tasks to use tools like
leaks on macOS, which can run a process and print a list of leaks detected at exit:

leaks -atExit ./test-libmongoc --no-fork

Another tool on macOS that looks interesting is libgmalloc, which overrides the behavior of malloc and detects memory errors like use-after-free. man libgmalloc shows how to use this with:

DYLD_INSERT_LIBRARIES=/usr/lib/libgmalloc.dylib ./test-libmongoc --no-fork

We also can research memory checking command line tools for Windows.