Use xcodebuild app thinning report in perf tests to track size of iOS apps over time

[jmagman]

Description

The perf tests currently tars the iOS ipa as a proxy for final app size. Instead, an "app thinning report" could be generated from a xcarchive:

xcodebuild -exportArchive -archivePath  /path/to/xcarchive -exportPath /path/to/export/location -exportOptionsPlist ExportOptions.plist

See xcrun xcodebuild -h for the valid export options plist keys. This was the plist I used for veggieseasons:

$ plutil -p ExportOptions.plist 
{
  "method" => "ad-hoc"
  "thinning" => "<thin-for-all-variants>"
}

(The "thinning" value should probably be a specific hardware string like "iPhone10,1" to trade-off for test time).

This command generates the ipas, as well as a App Thinning Size Report.txt and app-thinning.plist.

Also see "Getting app size report" in this tutorial.

[jmagman]

Also created is a ExportOptions.plist which contains the values from the passed in plist, merged with the default values. This is what was generated for me when I ran this on veggieseasons:

$ plutil -p /path/to/export/ExportOptions.plist 
{
  "compileBitcode" => 1
  "method" => "ad-hoc"
  "signingStyle" => "automatic"
  "stripSwiftSymbols" => 1
  "teamID" => "S8QB4VV633"
  "thinning" => "<thin-for-all-variants>"
}

\cc @dnfield

[dnfield]

When we do this, we should further otool or something on the resulting library to make sure that the install name is still valid after building bitcode.

[jmagman]

This would be nice to have as a tool feature so end users can see app release size, too.