`__IAR_SYSTEMS_ICC__` provides additional version information that
we need to determine correct usage of the compiler. Extract and
store it as `CMAKE_<LANG>_COMPILER_VERSION_INTERNAL`.
Issue: #17264
Make the implementation for this compiler more complete.
IAR has multiple C++ modes, historically they were reduced c++ versions
for embedded that gradually improved to the full standard (which can be
reduced again by e.g. disabling rtti and exceptions). The new
implementation picks the best available, but the c++ mode can also be
overridden by defining `CMAKE_IAR_CXX_FLAG`.
Add C/C++ standard flags so that all modes up to and including the last
supported standard are defined.
Fixes: #16826
This will allow sharing of the logic of the order to test compilers in
and the preprocessor macros used to do that and to determine the
version components.
Felipe Torrezan