ExternalReconfigure builds a one-file C library from a local repository
as a CMake external, then plants a file in its build directory to stand
for what an old configure left. Built again with the same inputs, the
directory is kept. With its recorded inputs rewritten the way another
crafter-build's configure would have left them, the next build has to
start from an empty directory and build the library again. Before the
fix the planted file survived the reconfigure.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
