Option to link against MIMALLOC statically

[DubbleClick]

We should add libmimalloc and then in the end link mimalloc.o (yes .o) before all other libs.

The option should work with both musl and glibc.

Mimalloc is much faster than musl libc's allocator in threaded scenarios and even faster than glibc's allocator. While a glibc targeted build can easily load mimalloc with LD_PRELOAD, it would be more convenient to offer a static linking option for it.

cc @dunglas

[DubbleClick]

Note that Microsoft recommends going with LD_PRELOAD if possible.

I think this should only be used for musl-libc static builds as it will cause issues if an extension is loaded dynamically that did not link against mimalloc.