[juxtapose]

I think I'm for Turing-completeness. Let me try to give my reasons...

1. No, using Turing-complete scripts does not prevent information extraction and meaningful automation. You can ask the program to dump useful information, e.g. targets, compiler flags, etc. That's what rizsotto/Bear does for Makefile. CMAKE_EXPORT_COMPILE_COMMANDS is another example.

2. I don't really think you can do anything further with declarative build languages, unless it is a really limited one like JSON or XML. Meson (a relatively advanced one in the space) advocates for non-Turing-completeness, but you still cannot, for example, modify meson build files reliably using an external tool other than a text editor.

3. Complex build configuration usually requires non-trivial computation and/or dynamic dependency graph building. Turing-completeness gives you a possibility and you don't need to wait for build tool upgrades.

Comparing Meson to CMake, I find the niceties of Meson are usually not inherently non-TC. That is, you can theoretically reimplement a nicer CMake with all the niceties of Meson, while still being TC.