fix: skip libutil on SunOS

libutil is not available on Solaris variants, even on Solaris 11 where
forkpty is available.

src/nvim/CMakeLists.txt

@@ -468,9 +468,11 @@ list(APPEND NVIM_LINK_LIBRARIES
 
 if(UNIX)
   list(APPEND NVIM_LINK_LIBRARIES
-    m
-    util
-  )
+    m)
+  if (NOT CMAKE_SYSTEM_NAME STREQUAL "SunOS")
+    list(APPEND NVIM_LINK_LIBRARIES
+      util)
+  endif()
 endif()
 
 set(NVIM_EXEC_LINK_LIBRARIES ${NVIM_LINK_LIBRARIES} ${LUA_PREFERRED_LIBRARIES})