I don't think build systems add -fPIC automatically, nor remove it automatically. C++ build systems do not stoop to the question of how to best build a C++ program, by and large. They are more task graph executors - either bad ones, like make, or good ones, like Bazel, but mostly task graph executors; the most "C++ support" you will get is native support for scanning #include files (as opposed to doing it yourself like make forces you to.)
GNU Autotools do, if you tell, that you have a shared library. You can also switch between static/dynamic linking at build time and if you also use GNU Libtool, it will figure out the flags of your build platform at build time.
> as opposed to doing it yourself like make forces you to
You can definitely don't have to do that. GNU Automake does it by default, but if you are using plain Make, you can also use makedepend or the appropriate flags of your compiler.
> either bad ones, like make
What is wrong/missing with make as a task graph executor?
> or good ones, like Bazel
What can Bazel do better?
I want to build a "standard library" for my build system that would stoop to that. I can do that because my build system is not just a task graph executor; it is backed by a full programming language and can add its own libraries to that language. IOW, I can add a `cpp` package to the build system that implements support for how to best build a C++ program.
So if you have a wishlist for that support, I'd love to hear it.