Replaced HAVE_DX with HAVE_DX9

panda/src/dxgsg9/Sources.pp

@@ -1,4 +1,4 @@
-#define BUILD_DIRECTORY $[HAVE_DX]
+#define BUILD_DIRECTORY $[HAVE_DX9]
 
 #define OTHER_LIBS \
    interrogatedb:c dconfig:c dtoolconfig:m \