mac: remove obsolete patch

tools/osx/libiconv_1.16_rt.patch

@@ -1,31 +0,0 @@
-diff --git a/lib/iconv.c b/lib/iconv.c
-index b7a04f8..41c5896 100644
---- a/lib/iconv.c
-+++ b/lib/iconv.c
-@@ -610,5 +610,26 @@ strong_alias (libiconv_open, iconv_open)
- strong_alias (libiconv, iconv)
- strong_alias (libiconv_close, iconv_close)
- #endif
-+
-+#undef iconv_open
-+#undef iconv
-+#undef iconv_close
-+
-+LIBICONV_DLL_EXPORTED iconv_t iconv_open (const char* tocode, const char* fromcode)
-+{
-+  return libiconv_open(tocode, fromcode);
-+}
-+
-+LIBICONV_DLL_EXPORTED size_t iconv (iconv_t icd,
-+                                    ICONV_CONST char * * inbuf, size_t *inbytesleft,
-+                                    char * * outbuf, size_t *outbytesleft)
-+{
-+  return libiconv(icd, inbuf, inbytesleft, outbuf, outbytesleft);
-+}
-+
-+LIBICONV_DLL_EXPORTED int iconv_close (iconv_t icd)
-+{
-+  return libiconv_close(icd);
-+}
-
- #endif