CUDA compilation fails with __builtin_is_constant_evaluated in boost/core/bit.hpp

[Michael-Preisel]

Description:

• Boost Version: 1.89.0
• CUDA Version: 12.6
• MSVC Version: 2022 (1925+)
• Error: "variable in constexpr function is uninitialized" for unsigned long r;

Root Cause:
Line 35 enables BOOST_CORE_HAS_BUILTIN_ISCONSTEVAL for MSVC 1925+ but doesn't exclude CUDA compiler (nvcc), which has stricter constexpr requirements.

Proposed Fix:
Change line 42 from:
#if defined(BOOST_MSVC) && BOOST_MSVC >= 1925
to:
#if defined(BOOST_MSVC) && BOOST_MSVC >= 1925 && '!defined(__CUDACC__)'

Impact: Prevents CUDA compilation errors while maintaining optimization for regular MSVC builds.