Update libmultiprocess subtree to improve build and logs #33322

1. 
   ryanofsky commented at 8:51 pm on September 5, 2025: contributor

   Includes:

   • https://github.com/bitcoin-core/libmultiprocess/pull/197
   • https://github.com/bitcoin-core/libmultiprocess/pull/202
   • https://github.com/bitcoin-core/libmultiprocess/pull/203
   • https://github.com/bitcoin-core/libmultiprocess/pull/200
   • https://github.com/bitcoin-core/libmultiprocess/pull/205

   These changes should give better feedback when there are build errors, and also make IPC logs more readable.

   The changes can be verified by running test/lint/git-subtree-check.sh src/ipc/libmultiprocess as described in developer notes and lint instructions

2. Squashed 'src/ipc/libmultiprocess/' changes from 1b8d4a6f1e54..13424cf2ecc1

   13424cf2ecc1 Merge bitcoin-core/libmultiprocess#205: cmake: check for Cap'n Proto / Clang / C++20 incompatibility
   72dce118649b Merge bitcoin-core/libmultiprocess#200: event loop: add LogOptions struct and reduce the log size
   85003409f964 eventloop: add `LogOptions` struct
   657d80622f81 cmake: capnproto pkg missing helpful error
   d314057775a5 cmake: check for Cap'n Proto / Clang / C++20 incompatibility
   878e84dc3030 Merge bitcoin-core/libmultiprocess#203: cmake: search capnproto in package mode only
   1a85da5873c2 Merge bitcoin-core/libmultiprocess#202: doc: correct the build instructions for the example
   df01873e1ecb Merge bitcoin-core/libmultiprocess#197: ci: Add freebsd and macos build
   3bee07ab3367 cmake: search capnproto in package mode only
   b6d3dc44194c doc: correct the build instructions for example
   fa1ac3000055 ci: Add macos and freebsd task
   
   git-subtree-dir: src/ipc/libmultiprocess
   git-subtree-split: 13424cf2ecc1e5eadc85556cf1f4c65e915f702a

   a334bbe9b7
3. Merge commit 'a334bbe9b79ddf1999003c792bc8945639b7e9c1' into pr/subtree-4 a4ee70e5b6
4. 
   DrahtBot commented at 8:52 pm on September 5, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33322.

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5. 
   Sjors commented at 10:10 am on September 6, 2025: member

   Windows error seems to be a failing download of one of the previous release binaries, but would be good to re-run it.

   Assuming that passes:

   ACK a4ee70e5b69c67c9caea1e97cb5b08f80536c7d3

6. fanquake added this to the milestone 30.0 on Sep 6, 2025
7. fanquake merged this on Sep 8, 2025
8. fanquake closed this on Sep 8, 2025

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Contributors
ryanofsky DrahtBot Sjors

Milestone
30.0