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

diff -wpruN --no-dereference '--exclude=*.orig' a~/gold/output.cc a/gold/output.cc
--- a~/gold/output.cc	1970-01-01 00:00:00
+++ a/gold/output.cc	1970-01-01 00:00:00
@@ -131,7 +131,7 @@ gold_fallocate(int o, off_t offset, off_
   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);