Ninja: Restore support for compilers not defining a C++ standard level
Since commit 386465bf83 (cmTarget: add support for C++ module fileset
types, 2022-04-08, v3.25.0-rc1~624^2~7), the Ninja generator checks for
C++20 support using logic that requires `CMAKE_<LANG>_STANDARD_DEFAULT`
to be non-empty. On some compilers, such as ARMClang, CMake does not
automatically detect and set default language standards, thus causing
`HaveStandardAvailable` to raise an internal error.
To fix this issue, if `CMAKE_CXX_STANDARD_DEFAULT` is empty, assume all
standards to be supported instead of calling `HaveStandardAvailable`.
This is consistent with how `CompileFeaturesNode::Evaluate` handles this
case.
Fixes: #24146
1 file changed
