imported from OmniOS
Probably it's to avoid C++ namespace damage

--- binutils-2.43.1/gold/output.cc.orig
+++ binutils-2.43.1/gold/output.cc
@@ -131,7 +131,7 @@
   if (len <= 0)
     return 0;
 
-#ifdef HAVE_POSIX_FALLOCATE
+#if defined(HAVE_POSIX_FALLOCATE) && !defined(__illumos__)
   if (parameters->options().posix_fallocate())
     {
       int err = ::posix_fallocate(o, offset, len);