[samooth]

The header preprocessor (which generates c/loadable-ext-*.h) was broken since the 0.16 Io.

Reader migration — readAlloc always failed, dump() was never called, and CI never exercised the consumer path.

Rewrite as a standalone host executable that takes paths via stdin.

Also bumps SQLite to 3.53.4, regenerates the committed headers, and fixes the CI matrix.

Depends on PR2 (feat/compat-0.16-0.17) for the cross-compile legs.

[vrischmann]

Why exactly do you change it to a standalone executable ?

[samooth]

Good question. The standalone executable was an intermediate attempt, not the final approach.

The inline custom build step was broken in three ways: readAlloc always failed against the new 0.16/0.17 Io.Reader API, processor.dump() was never called (so the output was just a 47-byte comment banner), and the consumer path never depended on the preprocess step. I first tried moving the logic into a small host executable to sidestep the cross-version Build-step/Io API differences and to pass paths via stdin (avoiding argv quoting issues on Windows/POSIX).

After fixing the inline step instead — readFileAlloc, actually calling dump(), and adding the dependency — the standalone executable was no longer needed, so the later commits reverted to the upstream-style inline PreprocessStep. The current PR head no longer builds or uses a standalone executable; I'll squash/reword the commits so the history doesn't imply otherwise.