Building Boost opens Visual Studio IDE

[YaroslavPuhach]

Attempting to run b2 or b2 --toolset=msvc opens Visual Studio many times instead of actually building Boost. The behavior was noticed with Visual Studio 2026 and does not seem to depend on the version of Boost in use. Tested with 1.76, 1.89, and 1.90.

[github-actions]

Thank you for your contributions. Main development of B2 has moved to https://github.com/bfgroup/b2 Please consider following up at https://github.com/bfgroup/b2/issues