Makefile: fix small bug

Symlink syntax caused java_gen/pre-written/src/src to be created
diff --git a/Makefile b/Makefile
index 4712a04..7b241c3 100644
--- a/Makefile
+++ b/Makefile
@@ -72,7 +72,7 @@
 	mkdir -p ${OPENFLOWJ_WORKSPACE}
 	ln -sf ../java_gen/pre-written/pom.xml ${OPENFLOWJ_WORKSPACE}/pom.xml
 	ln -sf ../java_gen/pre-written/LICENSE.txt ${OPENFLOWJ_WORKSPACE}/LICENSE.txt
-	ln -sf ../java_gen/pre-written/src ${OPENFLOWJ_WORKSPACE}/src
+	ln -sf ../java_gen/pre-written/src ${OPENFLOWJ_WORKSPACE}
 	rsync --checksum --delete -rv ${LOXI_OUTPUT_DIR}/openflowj/src/ ${OPENFLOWJ_WORKSPACE}/gen-src
 
 .loxi_ts.java: ${LOXI_PY_FILES} ${LOXI_TEMPLATE_FILES} ${INPUT_FILES} ${TEST_DATA}