with structuredAttrs lists will be bash arrays which cannot be exported
which will be a issue with some patches and some wrappers like cc-wrapper
this makes it clearer that NIX_CFLAGS_COMPILE must be a string as lists
in env cause a eval failure
Fixes#9044, close#9667. Thanks to @taku0 for suggesting this solution.
Now we have no modes starting with `/` or `+`.
Rewrite the `-perm` parameters of find:
- completely safe: rewrite `/0100` and `+100` to `-0100`,
- slightly semantics-changing: rewrite `+111` to `-0100`.
I cross-verified the `find` manual pages for Linux, Darwin, FreeBSD.
