The `-path` test of `find` does string comparison, not path comparison.
Hence, the format of `everythingFile` needed to be very specific. Now,
it can be denormalized (e.g. it can contain `/./`) and an error is
emitted if the everything file or its interface file can't be removed.
Upstream now provides a library file for the builtin library and ensured
that the existing interface files will be used regardless of whether
--local-interfaces is in effect. Hence, Agda will not try to write to
the Nix store anymore except if the build flags are changed.
The Everthing module is not part of a library and should therefore
not be copied to the nix store.
This is particularly bad, if the Everything module is defined in
an agda library included directory, e.g. consider an agda-lib with
include: .
and Everything.agda in the project root (.), in which case the
Everything module would become part of the library.
If multiple such projects are in the dependency tree, the Everything
module becomes ambiguous and the build would fail.
