How would I build a shared object file?

Trying to get my head around `bazel` is there a way of building a `tcmalloc.so` shared object file from this project?

I know the recommendation is just to compile applications with tcmalloc directly but for my use case: https://github.com/SamSaffron/allocator_bench I would like to do a side by side comparison to perftools and jemalloc that are LD_PRELOADed.

Also not against experimenting with a statically compiled ruby including tcmalloc, if we can prove it is faster / better maybe Ruby folks would be open to adding it.