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 looks like after a bump, CMake started passing `--git-dir=.git` as the first argument of `git rev-parse`.
But we do not really need to spoof `git` program now that Kaldi uses CMake’s `FetchContent` module.
We can just pass the path using configure flag directly:
https://cmake.org/cmake/help/latest/module/FetchContent.html#variable:FETCHCONTENT_SOURCE_DIR_%3CuppercaseName%3E
Git was also inadvertently used for generating `KALDI_PATCH_NUMBER`
in `VersionHelper`, to be potentially appended to `KALDI_VERSION`
but it was not actually being done by default.
We can set the variable directly to skip `VersionHelper`.
Also remove redundant `enableParallelBuild` since CMake enables it.
And drop separate `dev` output since Kaldi currently hardcodes
the `include/` directory so consumers would not be able to find them.
Splitting it out only removes 7 out of 303 MB.