The CheckSourceCompiles and CheckCompilerFlag would generally be preferred general
command syntax, but users may not realize they exist, so help point them there.
CMAKE_REQUIRED_FLAGS now notes that space-delimited string, not
;-list is required, which could be surprising compared to similar
options that do use ;-list
The old `check_X_source_runs` modules did not verify the arguments, so
we cannot start doing it now. Downgrade the hard error introduced in
commit 357e2ef429 (CheckSoureRuns: Add a unified way to check if a
source runs, 2020-09-14) via !5223 into a noisy warning.
The conversion of Check<Lang>CompilerFlag, SourceCompiles, and
SourceRuns over to the new functions has the possibility of breaking
projects that had functions with those existing names.
To reduce the possibility of collisions we now have all the
legacy code call functions that start with `cmake_`, and users
will need to explicitly include the new modules to get the
non-prefixed versions
Fixes: #21359
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>
