Originally WS_DISABLE_DEBUG was chosen to be
similar to G_DISABLE_ASSERT and NDEBUG.
However generator expressions are essential for modern CMake
but the syntax is weird and having to use negations makes it
ten-fold worse.
Remove the negation. Instead of changing the CMake variable
reverse the macro definition for WS_DISABLE_DEBUG.
The $<CONFIG:cgs> generator expression with multiple config arguments
requires CMake >= 3.19 so we can't use that yet for a further
syntactical simplification.