We run a `try_compile` with a tiny test source to check if the compiler
works so that we can fail early if it does not. When the compiler does
work, we immediately `try_compile` the ABI detection source. In the
common case that both steps work, we gain no useful information from the
first one and the work was wasted.
Re-order the checks to try the ABI detection first. If it works then
assume the compiler works and skip the dedicated check. If the ABI
check fails then proceed with the normal test for a working compiler so
the diagnostic can be shown as before.
Fixes: #18703
Add entries in Modules and Modules/Platform to support
Objective-C++ compiler determination and identification.
Add Modules to check Objective-C++ compiler flags, source
compilations, program checks, etc...
Use OBJCXX as the designator of the language, eg:
project(foo OBJCXX)
Add various tests for Objective-C++ language features. Add
tests to preserve C++ handling of .M and .mm files when
Objective-C++ is not a configured language.
Co-authored-by: Cristian Adam <cristian.adam@gmail.com>
