With the upstream patch to casadi (https://github.com/casadi/casadi/pull/3899),
There is no need for nixpkgs#mumps to symlink header files to subdir mumps.
Nix packagers should manualy specify the include directory and link libraries for
the coinmumps required project like nipxkgs#libopt.
The coin-or project ipopt use a thirdparty-mumps, this variant renames `libseq/mpi.h`
to `libseq/mumps_mpi.h` to avoid conflicts when building in a MPI environment.
See https://github.com/coin-or/Ipopt/blob/stable/3.14/ChangeLog.md?plain=1#L582.
Nix packagers don't need to worry about this cause we build in a sandbox environment.
For parrallel version of mumps built with mpi support, libseq is not needed and there will be no conflicts.
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"
```
