Cannot use @rules_foreign_cc//toolchains:current_cmake_toolchain in genrule

I'm attempting to run *only* the generate step of a cmake project, not actually build any targets, in order to generate a file created by `configure_file`. My best guess is I'd do this via a custom genrule, but I'm running into a pretty fundamental issue: `$(CMAKE)` isn't valid in a genrule with @rules_foreign_cc//toolchains:current_cmake_toolchain listed as one of the toolchains. Is this user error? The documentation seems to indicate that this rule is specifically meant for use in genrules.
Using bazel 5.1.1 for reference

Reproduce the custom genrule with Bazel 5.1.1 and @rules_foreign_cc//toolchains:current_cmake_toolchain. Start with the documentation for that toolchain and genrule variable expansion, then compare the documented behavior with the reported $(CMAKE) failure. Done means the generate-only workflow is confirmed and supported, or the limitation is clearly documented.

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