4.9.0

This release has mostly internal cleanups and restructuring. The most
significant being: fixing all memory leaks, automatic build system
startup with the boost-build rule, the Jam Python interfaces, and
the unmaintained Python build system port.

• Add minimal and debug options for optimization feature.
  -- René Ferdinand Rivera Morell
• Add Rocket Lake, Alder Lake, Sapphire Rapids and Zen 3 instruction sets.
  -- Andrey Semashev
• Remove all, on-exit, memory leaks and fix all ASAN errors.
  -- René Ferdinand Rivera Morell
• Remove use of boost-build.jam as a initialization configuration file.
  -- René Ferdinand Rivera Morell
• Remove the incomplete build system port and Jam engine Python support
  extensions.
  -- René Ferdinand Rivera Morell
• Fix not being able to do combined arm+x86 builds on macOS with darwin
  and clang toolsets.
  -- René Ferdinand Rivera Morell
• Fix not being able to do cross-compiles on macOS with clang toolset.
  -- René Ferdinand Rivera Morell
• Fix errors when collecting a large number of object files with long names
  into a static archive for gcc and clang toolsets.
  -- René Ferdinand Rivera Morell
• Fix detection of QCC in build.sh engine build script.
  -- René Ferdinand Rivera Morell
• Fix missing assembly flags for intel-win toolset.
  -- René Ferdinand Rivera Morell
• Fix possible command line length limit exceeded error with msvc toolset for
  link actions.
  -- René Ferdinand Rivera Morell
• New: Add a "t" mode to FILE_OPEN built-in rule that gives one the
  contents of a file when evaluated.
  -- René Ferdinand Rivera Morell

WARNING: This release removes the use of boost-build.jam and the
boost-build rule for initialization. The boost-build.jam is still
searched for and loaded to not break existing operations. But is considered
deprecated and will be removed in a future release.