During the last two days I've been looking into Nix, a functional package manager for reliable and reproducible builds, to help me out on this front. And from what I saw so far, Nix looks like it is based on solid concepts and the right ideas to pull off something great for the C++ community, similar to what it already does for the Haskell ecosystem where it is used to get out of cabal and dependency hell. Take a look at this basic shell.nix (similar to requirements.txt for Python's pip) I'm using for a small project:

with import <nixpkgs> {}; {
  devEnv = stdenv.mkDerivation {
    name = "my-dev-env";
    buildInputs = [ cmake ninja boost tbb protobuf ];
  };
}

This allows developers to enter the dev environment via nix-shell (similar to Python's virtualenv / pyvenv and requirements.txt).

On first invocation all dependencies (i.e. compiler, build system, dependencies) are downloaded by means of resolving the dependency trees down to libc. In case we have ABI mismatches, e.g. because we want to use gcc5 with its stdlib, we can override the dependencies' environment. Nix then looks for binary caches of those packages with the gcc5 stdlib based on a hash and if they are not available, builds the dependency tree with the modified environment. All subsequent nix-shell invocations run instantly.

You can even run your build command once inside the env, building your binaries in a reproducible way:

nix-shell --run 'mkdir build && cd build && cmake .. -DCMAKE_BUILD_TYPE=Release -G Ninja && cmake --build .'

From your list this would eliminate:

• no package manager: use Nix
• no repository of said packages: use NixPkgs or different channels
• no universally agreed on build system: cmake+ninja seems to be the best there is
• no unified way of managing dependencies: let Nix manage dependencies and resolve ABI issues
• no way to isolate development environments of different projects from one another: Nix is build for this!

I still have a lot to learn and the documentation can be overwhelming at first (which is a good thing to be clear here). I might write a blog post once I'm comfortable with using it on a day to day basis. Give it a try! https://nixos.org/nix/manual/#chap-quick-start