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"
```
Make Qt applications work on macOS Big Sur even if they're built with
an older version of the macOS SDK (<10.14 - we're currently using
10.12). This issue is fixed in 5.12.11, but it requires macOS SDK
10.13 to build. See https://bugreports.qt.io/browse/QTBUG-87014 for
more info.
The MKVToolNix GUI has been marked as unsupported on darwin since
88d7718a64 (mkvtoolnix-cli: fix build on darwin, 2017-03-13), but
currently it builds without issues. It is when mkvtoolnix-gui is run
that the window doesn't appear.
Setting the environment variable QT_MAC_WANTS_LAYER=1 fixes it and now
the GUI runs on Darwin too.
Tested on Big Sur.
Picked from 461466306e (octaveFull: set QT_MAC_WANTS_LAYER=1 on Darwin,
2021-07-22).
Use stdenv.mkDerivation instead of mkDerivation from libsForQt5, because
the latter forces the compiler to LLVM 5 on Darwin, which doesn't
support the new C++ filesystem library.
Fixes#132675.
Additional changes:
1. Qt is now needed for both the cli and gui variants.
2. Run the test suite
3. Drop a number of dependencies that are no longer needed
4. We have nlohmann_json and pugixml, so use those instead of the
vendored versions
5. Add support for reading chapters from DVDs
6. Build with rake as recommended by upstream
