VS: Restore support for CUDA with no optimization flags
Since !9270 (merged) we generate an
empty Optimization
element for the host compiler when there are no C
or C++ optimization flags enabled. The CUDA Toolkit Visual Studio
integration fails with an error if an empty string is inherited from the
host compiler's Optimization
element. If no CUDA optimization flags
are specified, write an explicit empty Optimization
element for the
CUDA compiler too.
Fixes: #26144 (closed)
Backport: release