FTBFS ICC on Windows: "QV4::Managed::Managed()" [..] is inaccessible

Intel Issue ID: 6000127929.
Intel task number: DPD200375809.

When compiling QtQml with ICC on Windows, the compilation stops with the following error:

qv4context_p.h(141): error #373: "QV4::Managed::Managed()" (declared at line 114 of "qv4managed_p.h") is inaccessible
  struct Q_QML_EXPORT ExecutionContext : public Managed
                                                ^
          detected during:
            implicit generation of "QV4::ExecutionContext::ExecutionContext()" at line 199
            implicit generation of "QV4::CallContext::CallContext()" at line 199

The reason for this seems to be an incompatibility between how ICC and how MSVC treat __declspec(dllexport classes: since the classes derived from QV4::Managed do not have their constructors deleted, they are implicit and are thus instantiated so they can be exported. Of course, that instantiation fails: MSVC silently discards the failed instantiation but ICC complains.