Comment by einpoklum
If TCMalloc uses bazel, then you build it with Bazel. It just needs to install itself where you tell it to, and then either it has given you a pkg-config file, or otherwise, your own build system needs some library-finding logic for it ("find module" in CMake terms). Or - are you saying the problem is that you need to install Bazel?
Building complete, optimised binaries can be much more complicated than just linking in a SO/A file. Things like cross-language LTO and PGO can be massive for performance and require integration throughout the build system.