Disable bindgen's autowatch of cloned includes in outdir

[bleggett]

.parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))

makes bindgen autowatch every header the build.rs clones into OUT_DIR.

This can force spurious rebuilds if a cloned header in OUT_DIR gets touched with a new mtime, or whatever.

But we can just turn this off and only trigger rebuilds on:

    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=inc/libscap.h");

this ought to be safe because the cloned files in OUT_DIR are transient, and you can't update the clone ref without touching build.rs itself (which would rerun) - so we really don't need to care about triggering rebuilds if the cloned libscap source headers change.

This will not guard against someone or something locally munging files in OUT_DIR and breaking their own build/local OUT_DIR corruption/etc, but that's not likely and if it did happen, a cargo clean would resolve it anyway.

[tycho]

Hmm, I'd still like to figure out the root cause of why scap.h had a newer timestamp than the output somehow. I couldn't find anything obvious in the source tree that would explain why its mtime was modified after the build finished.

The workaround seems simple enough though.

[bleggett]

Hmm, I'd still like to figure out the root cause of why scap.h had a newer timestamp than the output somehow. I couldn't find anything obvious in the source tree that would explain why its mtime was modified after the build finished.

Yeah I couldn't either. Nothing any of our (or Falco's build scripts) are doing should cause mtime updates AFAICT. How exactly are you reproducing/inducing the spurious rebuilds? I haven't been able to/haven't noticed spurious rebuilds but I might not be doing exactly what you're doing.