D81347 changes the ASTFileSignature to be an array of 20 uint8_t instead of 5 uint32_t.
However, it didn't update the code in ObjectFilePCHContainerOperations that creates
the dwoID in the module from the ASTFileSignature (Buffer->Signature being the
array subclass that is now std::array<uint8_t, 20> instead of std::array<uint32_t, 5>).
uint64_t Signature = [..] (uint64_t)Buffer->Signature << 32 | Buffer->Signature
This code works with the old ASTFileSignature (where two uint32_t are enough to
fill the uint64_t), but after the patch this only took two bytes from the ASTFileSignature
and only partly filled the Signature uint64_t.
This caused that the dwoID in the module ref and the dwoID in the actual module no
longer match (which in turns causes that LLDB keeps warning about the dwoID's not
matching when debugging -gmodules-compiled binaries).
This patch just unifies the logic for turning the ASTFileSignature into an uint64_t which
makes the dwoID match again (and should prevent issues like that in the future).