DatePlot project doesn't build because it's using the Swift package

[DivineDominion]

I noticed that Carthage fails in Xcode 13.4.1 and 14.0:

Packages are not supported when using legacy build locations, but the current project has them enabled.

The examples/DatePlot/DatePlot.xcodeproj is being used by Carthage -- which is probably also not correct, but that's another issue.

The DatePlot.xcodeproj also provides the same error in Xcode directly.

All the other example projects work fine since they don't use the Swift package output.

Full error message

$ carthage build --no-skip-current
*** xcodebuild output can be found in /var/folders/62/8k21681d08z9lhq8h433z3rh0000gp/T/carthage-xcodebuild.orx6Mt.log
A shell task (/usr/bin/xcrun xcodebuild -project /Users/ctm/Downloads/core-plot/examples/DatePlot/DatePlot.xcodeproj CODE_SIGNING_REQUIRED=NO CODE_SIGN_IDENTITY= CARTHAGE=YES -list) failed with exit code 74:
2022-10-14 08:51:29.997 xcodebuild[4301:1524260] Requested but did not find extension point with identifier Xcode.IDEKit.ExtensionSentinelHostApplications for extension Xcode.DebuggerFoundation.AppExtensionHosts.watchOS of plug-in com.apple.dt.IDEWatchSupportCore
2022-10-14 08:51:29.997 xcodebuild[4301:1524260] Requested but did not find extension point with identifier Xcode.IDEKit.ExtensionPointIdentifierToBundleIdentifier for extension Xcode.DebuggerFoundation.AppExtensionToBundleIdentifierMap.watchOS of plug-in com.apple.dt.IDEWatchSupportCore
xcodebuild: error: Could not resolve package dependencies:
  Packages are not supported when using legacy build locations, but the current project has them enabled.

[DivineDominion]

The folks at Flutter had similar problems with CI:
flutter/flutter#76868 (comment)

Some answers on the web say it's an Xcode bug. 🤷

I've messed with the build settings and removed the xcuserdata/ subfolders to no avail.

I've changed the Xcode-generated DatePlot.xcodeproj/project.xcworkspace/xcuserdata//MYUSERNAME.xcuserdatad/WorkspaceSettings.xcsettings file to use the value the Flutter folks recommend, changing

<key>BuildLocationStyle</key>
<string>UseTargetSettings</string>

to

<key>BuildLocationStyle</key>
<string>UseAppPreferences</string>

Since the Xcode prefs in my case use the new build system, this seems to win.

That's not a real fix, though.

[eskroch]

Fixed on the release-2.4 branch.

[DivineDominion]

Sweet, thanks for the maintenance effort!