Prevent an

 /usr/gcc/5/lib/gcc/x86_64-pc-solaris2.12/5.4.0/include-fixed/sys/feature_tests.h:399:2: error: #error "Compiler or options invalid for pre-UNIX 03 X/Open applications   and pre-2001 POSIX applications"

error.

This change should be passed upstream.

--- cmake-3.7.2/Utilities/cmlibuv/CMakeLists.txt.orig	2017-03-06 09:09:28.736859634 +0000
+++ cmake-3.7.2/Utilities/cmlibuv/CMakeLists.txt	2017-03-06 09:09:37.572534409 +0000
@@ -218,7 +218,7 @@
     )
   list(APPEND uv_defines
     __EXTENSIONS__
-    _XOPEN_SOURCE=500
+    _XOPEN_SOURCE=600
     )
   list(APPEND uv_sources
     src/unix/sunos.c