[llvm] [llvm][CMake] Check dependency cxx source compiles (PR #68549)

[Jonas Devlieghere via llvm-commits]

JDevlieghere wrote:

> LLVM has C API bindings, so it's possible that a user would only enable the C language. Unconditionally using `check_cxx_source_compiles` would fail due to a missing C++ compiler.

These modules are used when configuring the LLVM build itself. Can you really do that with just a C compiler? I'm aware of the bindings but without a C++ compiler, you can't build the thing it's binding in the first place. So is there  a configuration mode where you only build the C bindings against a pre-built LLVM? Is libffi or terminfo used in those C bindings?

https://github.com/llvm/llvm-project/pull/68549