Set policy CMP0025 to NEW within KWSys

KWSys does not depend on the Apple Clang compiler id being "Clang" so
set the policy to NEW explicitly to avoid the warning and get the NEW
behavior.

Change-Id: I884a82876ced444753a28eec1a2a26cc8c07cdef

CMakeLists.txt

@@ -85,6 +85,9 @@
 # written.
 
 CMAKE_MINIMUM_REQUIRED(VERSION 2.6.3 FATAL_ERROR)
+IF(POLICY CMP0025)
+  CMAKE_POLICY(SET CMP0025 NEW)
+ENDIF()
 
 #-----------------------------------------------------------------------------
 # If a namespace is not specified, use "kwsys" and enable testing.