@MarcoFalke as a follow on to your comment here this PR should reduce the appveyor build times by approximately 20 minutes. From around 65 to around 45.

The reduction is down to building the Qt libraries without msvc compiler optimisations. As mentioned above, removing the optimisations was to help with ABI compatibility. The build time reduction was a welcome side effect.

@hebasto thanks for checking. If you have time could you do me a favour (it's a quick set up) and check the vcpkg binary caching feature on your appveyor account?

If so the steps are:

• On your appveyor project for bitcoin add two environment variables (this is on the appveyor settings not in the yml file):
  VCPKG_FEATURE_FLAGS manifests,binarycaching
  VCPKG_BINARY_SOURCES nuget,https://aaronrc.pkgs.visualstudio.com/bitcoin/_packaging/vcpkg-deps/nuget/v3/index.json,read
• Re-run the same commit you ran above.

The test is to see whether your build job pulls the pre-built vcpkg dependencies from my Azure devops account. The reason it may not is the way vcpkg generates the hash to determine whether the pre-built dependency is a match or not.

If the pre-built dependencies are used your build time should be closer to 30 minutes.

Concept ACK 2c69381

Haven't reviewed the code, nor have I tested if building locally on Windows still works

@sipsorcery

@hebasto thanks for checking. If you have time could you do me a favour (it's a quick set up) and check the vcpkg binary caching feature on your appveyor account?

Configured and checked: re-build has finished "in 30 min".

Configured and checked: re-build has finished "in 30 min".

Perfect, thanks!

Concept ACK 2c69381
Checked that this only touches the MSVC files.

@MarcoFalke if you think it's a good idea you can add the environment setting below to the Bitcoin Core appveyor job to further reduce the build time by between 10 and 15 minutes. As mentioned above this setting is better put in the Appveyor build job settings rather than in the yml file.

VCPKG_BINARY_SOURCES nuget,https://aaronrc.pkgs.visualstudio.com/bitcoin/_packaging/vcpkg-deps/nuget/v3/index.json,read

Unlike previous attempts at caching vcpkg dependencies this one should be more reliable:

• If a particular package doesn't have a matching nuget package it will be built from source,
• If a new dependency is added to the vcpkg.json file it will be built from source,
• If the Appveyor image gets updated the version hash of the vcpkg dependency changes and will cause it to be built from source,
• The stored nuget packages are treated as readonly with the above environment variable. It requires a manual script to be run to add new packages.

I've created a custom script to run as a standalone appveyor build job which builds the dependencies in vcpkg.json and stores the results as nuget packages in my Azure site. It would be trivial to switch to a different nuget storage location or even standard file storage if required. It's probably worth verifying that this approach does prove more reliable than previous attempts before expending too much effort.