doxygen fixup

Author: ptheywood

cmake/dependencies/doxygen.cmake

@@ -82,7 +82,7 @@ function(create_doxygen_target FLAMEGPU_ROOT DOXY_OUT_DIR XML_PATH)
         set(DOXYGEN_GENERATE_TODOLIST             NO)
         # Create doxygen target            
         if("${XML_PATH}" STREQUAL "")
-            if(not TARGET "docs")
+            if(NOT TARGET "docs")
                 set(DOXYGEN_GENERATE_HTML     YES)
                 set(DOXYGEN_GENERATE_XML      NO)
                 set(DOXYGEN_HTML_OUTPUT       docs)