fix(windows): add strcasecmp compatibility for MSVC builds

Windows MSVC uses _stricmp instead of POSIX strcasecmp.
Add define to utility.c to map strcasecmp to stricmp when
building with MSVC, fixing linker errors for ensure_output_extension.

This matches the same pattern used in ccx_encoders_helpers.c.

Author: Rahul-2k4

src/lib_ccx/utility.c

@@ -1,6 +1,11 @@
 #include <stdio.h>
 #include <signal.h>
 #include <string.h>
+
+#ifdef _MSC_VER
+#define strcasecmp stricmp
+#endif
+
 #include "lib_ccx.h"
 #include "ccx_common_option.h"
 #include "activity.h"