import-std

• The experimental gate for C++23's import std has been dropped.

• Variable CMAKE_CXX_MODULE_STD and property target CXX_MODULE_STD control the availability of import std for C++ targets.

• Read-only variable CMAKE_CXX_COMPILER_IMPORT_STD lists the C++ standard levels for which import std is available on the current toolchain.

• Variable CMAKE_CXX_STDLIB_MODULES_JSON sets a specific module metadata file which CMake will use for constructing import std instead of relying on automatic detection via the current C++ compiler.