Windows CI failing

[martinsaposnic]

windows CI fails with

= note: LINK : warning LNK4217: symbol 'secp256k1_context_static' defined in 'libbitcoinconsensus-a7c9d7f7f75153ff.rlib(1a51c285fd8afce5-secp256k1.o)' is imported by 'libbitcoinconsensus-a7c9d7f7f75153ff.rlib(0f7fe36486e2efc1-pubkey.o)' in function '"public: static bool __cdecl CPubKey::CheckLowS(class std::vector<unsigned char,class std::allocator<unsigned char> > const &)" (?CheckLowS@CPubKey@@SA_NAEBV?$vector@EV?$allocator@E@std@@@std@@@Z)'␍

note: `link.exe` returned an unexpected error

note: the Visual Studio build tools may need to be repaired using the Visual Studio installer

note: or a necessary component may be missing from the "C++ build tools" workload

error: could not compile `lightning-background-processor` (lib test) due to 1 previous error

After trying to reproduce locally in a windows virtual machine, I found that after merging commit d9a6641 from PR #3968, it fails with

  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: LINK : warning LNK4217: symbol 'secp256k1_context_static' defined in 'libbitcoinconsensus-4c00e6e310d58111.rlib(1a51c285fd8afce5-secp256k1.o)' is imported by 'libbitcoinconsensus-4c00e6e310d58111.rlib(0f7fe36486e2efc1-pubkey.o)' in function '"public: static bool __cdecl CPubKey::CheckLowS(class std::vector<unsigned char,class std::allocator<unsigned char> > const &)" (?CheckLowS@CPubKey@@SA_NAEBV?$vector@EV?$allocator@E@std@@@std@@@Z)'␍
          LINK : fatal error LNK1318: Unexpected PDB error; LIMIT (12) ''␍


error: could not compile `lightning-background-processor` (lib test) due to 1 previous error

Previous commit works: 269cff7
Offending commit: d9a6641

Hypothesis: I think the Joiner struct is too complex and big and it makes the linker explode. I thought of a few alternatives but they all sucked

[TheBlueMatt]

Looks like we need to switch to lld rust-lang/rust#141626 (comment)