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"
```
Semi-automatic update. These checks were done:
- built on NixOS
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-keyconv -h` got 0 exit code
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-keyconv --help` got 0 exit code
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-keyconv -V` and found version 2.4.0
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-keyconv -v` and found version 2.4.0
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-keyconv --version` and found version 2.4.0
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-util -h` got 0 exit code
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-util --help` got 0 exit code
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-util -V` and found version 2.4.0
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-util -v` and found version 2.4.0
- ran `/nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0/bin/softhsm2-util --version` and found version 2.4.0
- found 2.4.0 with grep in /nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0
- found 2.4.0 in filename of file in /nix/store/cs5ycqjsa2lklgx5slaja3gshxf2g7r5-softhsm-2.4.0
