There's a merged pull request on the void-packages repository

common: unset CMAKE_GENERATOR before sourcing templates
https://github.com/void-linux/void-packages/pull/37413

Description:
When building dependencies of packages this has to be unset to avoid using e.g. `CMAKE_GENERATOR="Unix Makefiles"` for a package which expected to build with the default of `make_cmd=ninja`, and would subsequently fail with `ninja: error: loading 'build.ninja': No such file or directory` during `do_build()` if `do_configure()` generated a Makefile instead of a
build.ninja file.

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