The IAR compiler test works when a project specifies LANGUAGES C CXX
but fails if CXX comes before C. This change makes it work regardless
of the order.
Some are user facing.
Found using
codespell -q 3 --skip="./Utilities" -I .cmake-whitelist.txt`
whereby the whitelist contained:
ans
dum
helpfull
emmited
emmitted
buil
iff
isnt
nto
ot
pathes
substract
te
todays
upto
whitespaces
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
