Experiment: consider statically-linking jemalloc/mimalloc for glibc-based Linux

[lovell]

Now that this repo builds a statically-compiled shared library, we might want to consider also statically-linking an alternative memory allocator for glibc-based Linux to help avoid memory fragmentation.

lovell/sharp#955 provides some context.

(We might want look at e.g. redis to see how it is built.)

We should also investigate mimalloc built with its security features to see what overhead, if any, the guard pages add.