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"
```
libopenconnect >=9.00 added support for a DEFAULT_EXTERNAL_BROWSER build value
that enables support for using xdg-open to spawn an external browser from
consumers of the library such as GNOME/NetworkManager-openconnect. This
functionality is needed to support external browser SAML authentication flows
for various VPN protocols supported by libopenconnect.
The old build was failing on darwin because yubikey needs the PCSC framework dependency. I also upgraded to the latest vpnc-script as recommended on the openconnect homepage (see: https://www.infradead.org/openconnect/platforms.html). Lastly, I moved all dependencies which are not used at runtime from propagatedBuildInputs to buildInputs (Please correct me if that is wrong).
(cherry picked from commit 253f714f6b)
Forward-pick from staging to staging-next. It's quite small rebuild,
compared to what's caused by the parent commit.
