upgrade boost to 1.90

[MHN (monamaki)]

Bumps Boost from 1.87.0 (Linux) / 1.79.0 (Windows) to 1.90.0, and fixes a Windows build regression where bootstrap.bat was overwriting the Python configuration before b2.exe could use it.

Changes

• restore-packages.cmd — Reworks Windows Boost build:

  • Append Python config to project-config.jam after bootstrap.bat (bootstrap overwrites it, so pre-writing user-config.jam was silently ignored)
  • Restore CWD after bootstrap via cd /d %BOOST_ROOT% (bootstrap leaves the shell in tools\build\src\engine)
  • Simplify b2.exe flags: drop --prefix, --user-config, --debug-configuration; add address-model=64 link=static,shared threading=multi

• build-pythonextension-test.cmd — Update BOOST_VERSION / BOOST_VERSION_IN_UNDERSCORE to 1.90.0 / 1_90_0

• build-pythonextension-test.sh — Update default BOOST_ROOT to boost_1_90_0

• test/src/CMakeLists.txt — Update find_library suffixes for libboost_python and libboost_numpy from 1_79 → 1_90 (debug and release)

• README.md — Update Boost Python docs link to 1.90.0

[MHN (monamaki)]

Copilot can you review my PR?

[Copilot]

MHN (@monamaki) I've opened a new pull request, #71, to work on those changes. Once the pull request is ready, I'll request review from you.

[MHN (monamaki)]

Copilot can you write a Pull Request Description for my PR?

[Copilot]

MHN (@monamaki) I've opened a new pull request, #72, to work on those changes. Once the pull request is ready, I'll request review from you.