Allow for optional modules in build.

Change-Id: Ib99bfb3f92dfaa66dc2299db31b734adb5cceeca
Reviewed-on: https://asterix-gerrit.ics.uci.edu/768
Reviewed-by: Chris Hillery <ceej@lambda.nu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
diff --git a/.gitignore b/.gitignore
index 6453783..ced139e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -55,3 +55,6 @@
 dist
 *.iml
 .idea/
+asterixdb/asterix-opt
+*~
+