In preparation for the deprecation of `stdenv.isX`.
These shorthands are not conducive to cross-compilation because they
hide the platforms.
Darwin might get cross-compilation for which the continued usage of `stdenv.isDarwin` will get in the way
One example of why this is bad and especially affects compiler packages
https://www.github.com/NixOS/nixpkgs/pull/343059
There are too many files to go through manually but a treewide should
get users thinking when they see a `hostPlatform.isX` in a place where it
doesn't make sense.
```
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv.is" "stdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv'.is" "stdenv'.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "clangStdenv.is" "clangStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "gccStdenv.is" "gccStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenvNoCC.is" "stdenvNoCC.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "inherit (stdenv) is" "inherit (stdenv.hostPlatform) is"
fd --type f "\.nix" | xargs sd --fixed-strings "buildStdenv.is" "buildStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "effectiveStdenv.is" "effectiveStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "originalStdenv.is" "originalStdenv.hostPlatform.is"
```
It is somewhat curious that it behaves differently exclusively here, but
I don't think it is necessary to stop shipping a package due to floating
point arithmetic error—it would be unreasonable to assume there were
none…
See https://github.com/ekmett/ad/issues/113.
This hasn't been an issue on x86_64, but running it anyways shouldn't
hurt. aarch64-darwin's trouble could be due to codesigning? Besides that
there don't seem to be many differences between the actual derivations.
This also unbreaks the test suite of regex-rure.
This reverts commit 32eecc6cc9.
Reason for revert: This fix doesn't alleviate the problem in two ways:
1. It is in the aarch64-darwin section of configuration-darwin.nix,
the problem appears on x86_64-darwin (bytepatch doesn't support
aarch64).
2. When moving the override into the general *-darwin section, the
problem with bytepatch is also unaffected, see my attempt in
https://github.com/NixOS/nixpkgs/pull/217201.
