[test] missing include

ferdymercury · dpiparo · commit 1ab5c1a842cf · 2025-03-27T20:25:50.000+01:00
diff --git a/io/io/test/TFileMergerTests.cxx b/io/io/test/TFileMergerTests.cxx
@@ -8,6 +8,7 @@
 #include "TFile.h"
 #include "TTree.h"
 #include "TH1.h"
+#include "TSystem.h"
 
 #include <memory>
 
