crt: Define import symbol for UCRT _snwprintf() function

Signed-off-by: Martin Storsjö <martin@martin.st>

mingw-w64-crt/stdio/ucrt__snwprintf.c

diff --git a/mingw-w64-crt/stdio/ucrt__snwprintf.c b/mingw-w64-crt/stdio/ucrt__snwprintf.c
index 5f5a435..5e03d26 100644
--- a/mingw-w64-crt/stdio/ucrt__snwprintf.c
+++ b/mingw-w64-crt/stdio/ucrt__snwprintf.c
@@ -10,8 +10,6 @@
 #include <stdarg.h>
 #include <stdio.h>
 
-int __cdecl _snwprintf(wchar_t * restrict _Dest, size_t _Count, const wchar_t * restrict _Format, ...);
-
 int __cdecl _snwprintf(wchar_t * restrict _Dest, size_t _Count, const wchar_t * restrict _Format, ...)
 {
   va_list ap;
@@ -21,3 +19,4 @@
   va_end(ap);
   return ret;
 }
+int __cdecl (*__MINGW_IMP_SYMBOL(_snwprintf))(wchar_t * restrict, size_t, const wchar_t * restrict, ...) = _snwprintf;