Fix warning for Android NDK compiler: "function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]"

https://stackoverflow.com/questions/42125/warning-error-function-declaration-isnt-a-prototype
In C int foo() and int foo(void) are different functions. int foo() accepts an arbitrary number of arguments, while int foo(void) accepts 0 arguments. In C++ they mean the same thing.

src/cpuinfo/SDL_cpuinfo.c

@@ -1239,7 +1239,7 @@ void SDL_SIMDFree(void *ptr)
 
 #include <stdio.h>
 
-int main()
+int main(void)
 {
     printf("CPU count: %d\n", SDL_GetCPUCount());
     printf("CPU type: %s\n", SDL_GetCPUType());