Windows, compiling : Remove _DEBUG preprocessor constant, to fix debug build with older cmake.
Windows, compiling : Remove _DEBUG preprocessor constant, to fix
debug build with older cmake.

The constant is implicitely defined by VS when chosen C runtime is Debug
(/MTd, MDd).

CMake does not define it since https://public.kitware.com/Bug/view.php?id=15777
was fixed.

We remove it from compile flags, to be able to build Debug with /MT runtime
using older cmakes.

natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2