Add missing includes

They are needed, otherwise the next commit will not compile

src/index/base.cpp

@@ -9,6 +9,7 @@
 #include <shutdown.h>
 #include <tinyformat.h>
 #include <util/syscall_sandbox.h>
+#include <util/system.h>
 #include <util/thread.h>
 #include <util/translation.h>
 #include <validation.h> // For g_chainman

src/index/coinstatsindex.cpp

@@ -10,6 +10,7 @@
 #include <serialize.h>
 #include <txdb.h>
 #include <undo.h>
+#include <util/system.h>
 #include <validation.h>
 
 using kernel::CCoinsStats;