syncbase-java: add temporary makefile with javadoc rule

Change-Id: Ic814fc22026227d42e827578e068cb9bd4b79233
diff --git a/syncbase/Makefile b/syncbase/Makefile
new file mode 100644
index 0000000..19f86e7
--- /dev/null
+++ b/syncbase/Makefile
@@ -0,0 +1,10 @@
+# A quick and temporary Makefile, for frequent tasks during Syncbase Java API
+# development.
+
+SHELL := /bin/bash -euo pipefail
+
+# Note, javadoc complains about the self-closing <p/> tags that Android Studio
+# creates.
+javadoc:
+	javadoc -d /tmp/javadocs -sourcepath src/main/java -subpackages io || true
+	@echo "open file:///tmp/javadocs/index.html"