Fix error when compiling with -std=c++20

[nilsfriess]

While trying to fix the constexpr half problems I tried compiling the project with -std=c++20. Almost everything compiled expect for a function call to std::inserter in the cbs part: In C++20 the signature of std::inserter changed and the container that is used with std::inserter now requires a begin method (because the second argument of std::inserter now is of type std::ranges::iterator_t which is essentially defined as the type of ranges::begin(Container)). So I just added a begin function to the type it complains about (and since this type is just a wrapper for llvm::SmallPtrSet, I can just call begin of llvm::SmallPtrSet).

[illuhad]

Thanks!

[illuhad]

What is the relation between constexpr half and compiling our compiler components with -std=c++20?

[nilsfriess]

What is the relation between constexpr half and compiling our compiler components with -std=c++20?

Maybe I formulated it a bit confusing: I was trying to compile the project with C++20 to check if my changes to the half class (containing feature test macros to detect bit_cast capabilities) work. During compilation, I got the error explained above. So I just extracted the fix for this error as a separate PR, it has absolutely nothing to do with the half class :)