Disable linkat() on WASI.

Author: serhiy-storchaka

Modules/posixmodule.c

@@ -573,7 +573,11 @@ extern char *ctermid_r(char *);
 #  define HAVE_FACCESSAT_RUNTIME 1
 #  define HAVE_FCHMODAT_RUNTIME 1
 #  define HAVE_FCHOWNAT_RUNTIME 1
+#ifdef __wasi__
+#  define HAVE_LINKAT_RUNTIME 0
+# else
 #  define HAVE_LINKAT_RUNTIME 1
+# endif
 #  define HAVE_FDOPENDIR_RUNTIME 1
 #  define HAVE_MKDIRAT_RUNTIME 1
 #  define HAVE_RENAMEAT_RUNTIME 1