[Bug c++/123627] ICE using local lambda in module partition

[nshead at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123627

--- Comment #2 from Nathaniel Shead <nshead at gcc dot gnu.org> ---
Ah, but we cannot just mark as MK_unique because then we'll clash if a user has
a third TU:

  // c.cpp
  module repro;
  import :part;
  void use() {
    foo();
  }

because it'll need to dedup the type provided from the combined CMI with the
type provided from the partition...