nx_ccdiag_selftest.nx

nx_ccdiag_selftest.nx -- VALID no-op (was briefly a deliberately-broken module to prove nx_sov_build_run now auto-prints nx_cc's real stderr on an empty-.s failure; verified 2026-07-06: building a call to an undefined fn now surfaces "nx_parse: call to undefined function: ..." automatically instead of an opaque "empty .s"). Neutralised so it never trips a build sweep. To re-demo: add `let x = undefined_fn(0)` and rebuild. expect_exit:0