Fix #1328: ENABLE_HLSL=OFF breaking build.

CMakeLists.txt

@@ -95,8 +95,10 @@ endif()
 if(ENABLE_OPT)
     message(STATUS "optimizer enabled")
     add_definitions(-DENABLE_OPT=1)
-elseif(ENABLE_HLSL)
-    message(STATUS "spirv-tools not linked - illegal SPIRV may be generated for HLSL")
+else()
+    if(ENABLE_HLSL)
+        message(STATUS "spirv-tools not linked - illegal SPIRV may be generated for HLSL")
+    endif()
     add_definitions(-DENABLE_OPT=0)
 endif()