Use UNICODE wWinMain, to make CRT initialize __wargv.

PC/WinMain.c

@@ -5,10 +5,10 @@
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
-int WINAPI WinMain(
+int WINAPI wWinMain(
     HINSTANCE hInstance,      /* handle to current instance */
     HINSTANCE hPrevInstance,  /* handle to previous instance */
-    LPSTR lpCmdLine,          /* pointer to command line */
+    LPWSTR lpCmdLine,         /* pointer to command line */
     int nCmdShow              /* show state of window */
 )
 {