VS: Fix support for nvcc flags not in our flag table
The change in !996 (merged) accidentally appended to the AdditionalOptions
as if it were a ;
-separated list, but it is actually a command-line string. Append with a space instead.
While at it, fix the same problem for the AdditionalOptions
added to CudaLink
by !951 (merged).
Fixes: #17008 (closed)