cmake: Add _CRT_SECURE_NO_WARNINGS to all projects

This prevents issues with using standard C functions, where microsoft
would otherwise spit out pointless warnings to encourage using
microsoft-specific functions instead.

plugins/win-capture/inject-helper/inject-helper.c

@@ -1,5 +1,3 @@
-#define _CRT_SECURE_NO_WARNINGS
-
 #include <stdio.h>
 #include <stdlib.h>
 #include <wchar.h>