Add missing cassert includes

Bug: http://b/175635923
Test: treehugger
Change-Id: I8caf940f7b6e2fdd921516efea4aed14e0c2afb7
diff --git a/cmds/idmap2/libidmap2/Idmap.cpp b/cmds/idmap2/libidmap2/Idmap.cpp
index 6515d55..06650f6 100644
--- a/cmds/idmap2/libidmap2/Idmap.cpp
+++ b/cmds/idmap2/libidmap2/Idmap.cpp
@@ -17,6 +17,7 @@
 #include "idmap2/Idmap.h"
 
 #include <algorithm>
+#include <cassert>
 #include <iostream>
 #include <iterator>
 #include <limits>