5.4.0

This is the end of year release. Biggest new items are the detection of Visual Studio 2026 (aka msvc145).

• New: Add initial support for C++-26 Contracts for GCC based toolsets (like clang).
  -- René Ferdinand Rivera Morell
• New: Allow explicit target triple for clang-linux and clang-darwin.
  -- Dmitry Arkhipov
• New: Change documentation style to support light/dark user preference.
  -- René Ferdinand Rivera Morell
• New: Added the ability to escape the '$' character before '(' as "$$" which will allow using the "$()" and "$(())" expressions of bash, sh, and other shells.
  -- Ivan Kotov
• New: Added integration for vcpkg with distinct roots.
  -- Dmitry Arkhipov
• New: Add support for detecting and building with VS-2026 (AKA vs-18.0, aka msvc 14.5).
  -- Miuna, Zangetsu, René Ferdinand Rivera Morell
• Fix invoking asciidoctor on Windows.
  -- René Ferdinand Rivera Morell
• Fix, propagate dll-path to shared libraries.
  -- Dmitry Arkhipov
• Fix mpi compiler detection to detect not just the first one (mpi++).
  -- Samuel Debionne
• Fix flag options, that are not registered as args, not being recognized. Fixes --show-libraries in Boost build files.
  -- Dmitry Arkhipov
• Fix discovery and building with Python free-threaded variant.
  -- Zhang Wen
• Fix build issues with QNX compiolers.
  -- "fragarian"
• Add libstdc++ to stdlib feature as the current naming for that std library.
  -- Dmitry Arkhipov
• Fix building when targetting WASM64 with emscripten.
  -- Uilian Ries
• Fix resolution of subprojects of rooted projects.
  -- Dmitry Arkhipov
• Fix crash when using -d9 to output module debug stats.
  -- René Ferdinand Rivera Morell