Appveyor timing collection (PR #14109)
CI build times have been increasing.
Measurement of the build the times requires downloading the build log and manually looking for markers to assess the time taken.
Changes:
For developers, the Appveyor message should include a breakdown of the CI build times.
Approach:
Record times at various stages of the build to a CSV file (timing.csv)
At the end of the build, process the CSV file to calculate the minutes between each stage.
Post this information as an appveyor message + save as artifact.
