[llvm] [ConstantInt] Disable implicit truncation in ConstantInt::get() (PR #171456)

[Alexis Engelke via llvm-commits]

aengelke wrote:

I realize I'm a little late, but (a) this should've been in the release notes and (b) this also breaks IRBuilder::getIntN. This is even more unfortunate, as the assertion does not get triggered in release builds of LLVM, so the result is a silent miscompilation that can be hard to debug: https://godbolt.org/z/3xdncMxWx

For the next time we do breaking changes like this, we should probably add appropriate assertions to the header files as well.

https://github.com/llvm/llvm-project/pull/171456