[clangd] no parse context for objective-cpp files when OBJCXX enabled

when opening an objective-cpp file in a project that has OBJCXX enabled as a first-class cmake language, a header is shown: "Warning: This file is not part of any project [...]"

if objcxx however is not enabled as language, the file is properly parsed.

–

observations:

• if objcxx is enabled, the c++ code model inspector in the attached project only has a C++ context
• if objcxx is not enabled, the c++ code model inspector shows two parse contexts (C++ and Obj-C+, where Obj-C+ self-identifies as CXX17 with ObjectiveC language extensions