Add missing include

thanks to clang 10

src/mesh/LogicalConnectivityBuilder.cpp

@@ -6,6 +6,8 @@
 #include <utils/Array.hpp>
 #include <utils/Messenger.hpp>
 
+#include <unordered_map>
+
 template <size_t Dimension>
 inline void
 LogicalConnectivityBuilder::_buildBoundaryNodeList(const TinyVector<Dimension, uint64_t>&, ConnectivityDescriptor&)