stdlib: just cast iconv()'s 2nd arg to void *.

This makes the compiler happy (enough) regardless of whether the C runtime
headers think this argument should be const or not.

Fixes #4966.

src/stdlib/SDL_iconv.c

@@ -36,18 +36,6 @@
 #define LIBICONV_PLUG 1
 #endif
 #include <iconv.h>
-
-/* Depending on which standard the iconv() was implemented with,
-   iconv() may or may not use const char ** for the inbuf param.
-   If we get this wrong, it's just a warning, so no big deal.
-*/
-#if defined(_XGP6) || defined(__APPLE__) || defined(__RISCOS__) || defined(__FREEBSD__) || \
-    defined(__EMSCRIPTEN__) || \
-    (defined(__GLIBC__) && ((__GLIBC__ > 2) || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 2)) || \
-    (defined(_NEWLIB_VERSION)))
-#define ICONV_INBUF_NONCONST
-#endif
-
 #include <errno.h>
 
 SDL_COMPILE_TIME_ASSERT(iconv_t, sizeof (iconv_t) <= sizeof (SDL_iconv_t));
@@ -69,12 +57,9 @@ SDL_iconv(SDL_iconv_t cd,
           const char **inbuf, size_t * inbytesleft,
           char **outbuf, size_t * outbytesleft)
 {
-    size_t retCode;
-#ifdef ICONV_INBUF_NONCONST
-    retCode = iconv((iconv_t) ((uintptr_t) cd), (char **) inbuf, inbytesleft, outbuf, outbytesleft);
-#else
-    retCode = iconv((iconv_t) ((uintptr_t) cd), inbuf, inbytesleft, outbuf, outbytesleft);
-#endif
+    /* iconv's second parameter may or may not be `const char const *` depending on the
+       C runtime's whims. Casting to void * seems to make everyone happy, though. */
+    const size_t retCode = iconv((iconv_t) ((uintptr_t) cd), (void *) inbuf, inbytesleft, outbuf, outbytesleft);
     if (retCode == (size_t) - 1) {
         switch (errno) {
         case E2BIG: