While Guix eventually runs a builder script, the script is 1) a Guile script and 2) not directly provided by the user but the result of compilation.
Guix does not stitch shell scripts together. Builds in Guix are split into build phases, which are Guile procedures. Build system abstractions are collections of these procedures. A packager can inject additional build phases or delete existing build phases from these build systems on a package by package basis.
The `trivial-build-system` is used for packages where none of the existing build systems are applicable, not even with build phases removed or added. This works but is not used very often as it is often more convenient to start with something like the `gnu-build-system` and to replace phases by providing new procedures; this is done to benefit from build phases that the `gnu-build-system` provides, such as those that unpack the sources, patch shebangs, or validate the binaries.
Thanks for the Guix info, as I say I've not really used it. The use of "phases", etc. is what I was getting at w.r.t. Nix's complicated "autoconf/automake support" (AKA `stdenv.mkDerivation`).
As you say, Guix's use of Scheme rather than stiching shell scripts together should be more powerful (in particular, concatenating strings of bash results in a rather opaque builder; whilst a more declarative s-expression approach would make traversing and modifying the builder more feasible)
Guix does not stitch shell scripts together. Builds in Guix are split into build phases, which are Guile procedures. Build system abstractions are collections of these procedures. A packager can inject additional build phases or delete existing build phases from these build systems on a package by package basis.
The `trivial-build-system` is used for packages where none of the existing build systems are applicable, not even with build phases removed or added. This works but is not used very often as it is often more convenient to start with something like the `gnu-build-system` and to replace phases by providing new procedures; this is done to benefit from build phases that the `gnu-build-system` provides, such as those that unpack the sources, patch shebangs, or validate the binaries.