Well, you can expect that there is at least a compiler and runtime available compatible with the software you want to build; if your software is e.g. written in Java, then a build system also implemented in Java looks like a good fit. I usually develop in C++, so my preferred approach is to have a lean build system written in C89 which has only standard dependencies and compiles like "gcc buildsystem.c".

I don't know how you would write and deploy a build system when there is no implementation for the language it uses; this looks like an unsolvable bootstrap problem to me; you would need a precompiled build system to build the build system, and that on all platforms you want to build; and anyway I don't think that a build system language should be Turing complete (or otherwise the language should at least support modularization and static typing).

Bazel is certainly great for a lot of use cases, but it is one of those Google colossi where you have to hire a specialized team to manage and run your build. GN has a similar issue in that in practice there is an insurmountable dependency of a gazillion of Python scripts (depot tools and the like), even if GN and Ninja are written in C++ and only have standard dependencies.