Gexps are not a build system implementation. They are a means to generate code. Guix continues to use whatever build system a package requires, such as the GN

Gexps are not a build system implementation. They are a means to generate code. Guix continues to use whatever build system a package requires, such as the GNU build system, the CMake build system, the R build system, the Python build system, etc. Gexps are not an attempt to replace these build systems. They are a way to stage code on the host side that is meant to run on the build side; this could be done with mere S-expressions through quoting, but would require more boilerplate. Gexps provide additional context, which allows for simpler code.