Changes to the C library do not trigger a rebuild

[egrimley-arm]

If the C code in psa-crypto-sys/vendor/ is changed then cargo does not rebuild it.

A work-around is to run touch psa-crypto-sys/build.rs when the C code might have changed.

I think it would be better if build.rs found every file (and perhaps every directory) under vendor/ (there's a crate called walkdir) and emitted cargo:rerun-if-changed=PATH for each one. (Or you could try to more selective, but persuading cmake to tell you which files really matter would probably be too much work.)

[hug-dev]

Thanks for the report!

A work-around is to run touch psa-crypto-sys/build.rs when the C code might have changed.

oh wow I did not know that touch could do that! The name of the command now makes more sense 😄
The walkdir idea seems nice! If we do cargo:rerun-if-changed=vendor, will it detect any change inside the directory? I would say no by default, but maybe here it will since this is a git repository. I am also wondering if we can target a git file in .git (or .git itself) to check for any change.