COMP: More KWSys SharedForward pointer const-ness

This adds another cast to avoid pointer conversion warnings.
Unfortunately C does not recognize implicit conversions that add
cv-qualifiers as well as C++ does.

Source/kwsys/SharedForward.h.in

@@ -507,7 +507,7 @@ static void kwsys_shared_forward_execvp(const char* cmd,
   nargv[argc] = 0;
 
   /* Replace the command line to be used.  */
-  argv = nargv;
+  argv = (char const* const*)nargv;
   }
 #endif