doc: build: Fix instructions for msvc gui builds #31851

1. 
   davidgumberg commented at 9:01 pm on February 12, 2025: contributor

   If the instructions in doc/build-windows-msvc.md are followed as-is, and “Developer (PowerShell|Command Prompt) for VS 2022” is used to execute the suggested build commands, the root directory of vcpkg (e.g. in VS 2022 Community edition: C:\Program Files\Microsoft Visual Studio\2022\Community\VC\vcpkg), is too long, and when vcpkg attempts to build any of the QT packages, it will fail because of build steps that require path lengths greater than Windows’ MAX_PATH 260 character limit. This can be avoided without needing to move the vcpkg root dir by setting --x-buildtrees-root to a short path, like C:\vcpkg.

   See e.g. https://github.com/microsoft/vcpkg/issues/28451, https://github.com/microsoft/vcpkg/issues/28083, https://github.com/microsoft/vcpkg/issues/24751.

2. doc: build: Fix instructions for msvc gui builds

   If the instructions are followed as-is, and "Developer
   (PowerShell|Command Prompt) for VS 2022" is used to execute the
   suggested build commands, the root directory of vcpkg (e.g. in VS 2022
   Community edition: `C:\Program Files\Microsoft Visual
   Studio\2022\Community\VC\vcpkg`), is too long, and when vcpkg attempts
   to build any of the QT packages, it will fail because of build steps
   that require path lengths greater than Windows' `MAX_PATH` 260 character
   limit. This can be avoided without needing to move the vcpkg root dir by
   setting `--x-buildtrees-root` to a short path, like `C:\vcpkg`.

   c3fa043ae5
3. 
   DrahtBot commented at 9:01 pm on February 12, 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/31851.

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4. DrahtBot added the label Docs on Feb 12, 2025
5. hebasto added the label Windows on Feb 13, 2025
6. hebasto added the label Build system on Feb 13, 2025
7. 
   hebasto commented at 8:21 am on February 13, 2025: member

   My only concern is that --x-buildtrees-root=<path> is labeled as:

   an experimental feature of vcpkg which may change or be removed at any time.

8. 
   davidgumberg commented at 5:20 am on February 14, 2025: contributor

   I considered that, but this solution is much more sane than any of the others I managed to come up with, and the flag has been around for at least 4 years (https://github.com/microsoft/vcpkg/issues/13789#issuecomment-700140607) , and this is only documentation, if there is a better solution, especially one that doesn’t require the user to intervene in any way, that would be ideal.
9. hebasto approved
10. 
    hebasto commented at 7:42 am on February 14, 2025: member

    ACK c3fa043ae560289759b6f836ac62736d97ba91bf.
11. TheCharlatan approved
12. 
    TheCharlatan commented at 9:08 am on February 14, 2025: contributor

    ACK c3fa043ae560289759b6f836ac62736d97ba91bf

    Am I misremembering or was this, or a similar workaround, part of the previous build instructions at some point?

13. 
    davidgumberg commented at 8:40 pm on February 14, 2025: contributor

    ACK c3fa043

    Am I misremembering or was this, or a similar workaround, part of the previous build instructions at some point?

    Yep, #29048 added a similar note to the old build_msvc/README.md, which had instructions for doing a static build of Qt, but I guess during the cmake transition, there was a switch from manually building Qt to using vcpkg, but sadly, the same problem still exists.

14. 
    achow101 commented at 10:11 pm on February 14, 2025: member

    ACK c3fa043ae560289759b6f836ac62736d97ba91bf
15. achow101 merged this on Feb 14, 2025
16. achow101 closed this on Feb 14, 2025

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Contributors
davidgumberg DrahtBot hebasto TheCharlatan achow101

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