This change fixes Landlock Make so that only the output target file is
unveiled, rather than unveiling the directory that contains it. This
gives us a much stronger sandbox. It also helped identify problematic
build code in our repo that should have been using o/tmp instead.
Landlock isn't able to let us unveil files that don't exist. Even if
they do, then once a file is deleted, the sandboxing for it goes away.
This caused problems for Landlock Make because tools like GNU LD will
repeatedly delete and recreate the output file. This change uses the
compile.com wrapper to ensure on changes happen to the output inode.
New binary available on https://justine.lol/make/Fixes#528
We can put this back the moment someone requests it. Pain-free garbage
collection for the C language is pretty cool. All it does is overwrite
the return address with a trampoline that calls free(). It's not clear
what it should be named if it's made a public API.