Visual Studio 22 does not compile va_arg that are function pointers. …

…Instead, the function pointers must be a typdef. For what its worth, see https://stackoverflow.com/a/37114318.

spec/ffi/fixtures/ClosureTest.c

@@ -16,23 +16,23 @@
 
 double testClosureVrDva(double d, ...) {
     va_list args;
-    double (*closure)(void);
+    typedef double (*closure_fun)(void);
 
     va_start(args, d);
-    closure = va_arg(args, double (*)(void));
+    closure_fun closure = va_arg(args, closure_fun);
     va_end(args);
 
     return d + closure();
 }
 
 long testClosureVrILva(int i, long l, ...) {
     va_list args;
-    int (*cl1)(int);
-    long (*cl2)(long);
+    typedef int (*cl1_fun)(int);
+    typedef long (*cl2_fun)(long);
 
     va_start(args, l);
-    cl1 = va_arg(args, int (*)(int));
-    cl2 = va_arg(args, long (*)(long));
+    cl1_fun cl1 = va_arg(args, cl1_fun);
+    cl2_fun cl2 = va_arg(args, cl2_fun);
     va_end(args);
 
     return cl1(i) + cl2(l);