[net6] Fix ILStrip'ed apps to actually work again

[chamons]

Fixes: #13094

• In a late minute change to the ILStrip PR ([msbuild] Add ILStrip'ing for net6 applications. Fixes #11445. #12563) a change to support XVS support broke execution of Apps that were stripped
• Applications were broken because none of the stripped assemblies were actually copied into the bundle
• However, the tests still passed, because all assemblies that were there had no IL (zero assemblies total)

Now why did this happen?

• The stripped assemblies were changed to return via an msbuild Output Element
• Output Element can return an Property or ItemGroup, depending if you use the PropertyName or ItemName attributes
• Unfortunately I used PropertyName, when I expected an ItemGroup. So I silently had a property created instead.
• Thus zero items were added to the list of files to copy into the bundle
• Which was undetected as the test did not confirm files were copied in, and manual tests were not run so late into the PR (3 weeks after PR was opened)

How was it fixed?

• Correctly using ItemName on Output created a valid item group to reference
• However, that still failed with an absurdly confusing error:

 PATH/Microsoft.NET.Publish.targets(277,5): error MSB3024: Could not copy the file FILE to the destination file PATH, because the destination is a folder instead of a file. To copy the source file into a folder, consider using the DestinationFolder parameter instead of DestinationFiles.

• After a splunking through netcore targets, I found the metadata on these assemblies references really matters. Without it, they are not processed correctly at all.
• Thus, I updated ILStripBase to clone the existing metadata when changing the original assembly reference to the stripped path
• Finally, I corrected the test to assert that required files are copied in. I also manually ran our device test.

[vs-mobiletools-engineering-service2]

❌ [PR Build] Tests failed on Build ❌

Tests failed on Build.

• Azure DevOps
• Html Report (VSDrops)

API diff

✅ API Diff from stable

View API diff

• iOS vsdrops gist
• macOS vsdrops gist
• tvOS vsdrops gist
• watchOS vsdrops gist
• macCatiOS vsdrops gist
• macCat vsdrops gist

View dotnet API diff

• dotnet-iOS vsdrops gist
• dotnet-macOS vsdrops gist
• dotnet-tvOS vsdrops gist
• dotnet-MacCatalyst vsdrops gist

View dotnet legacy API diff

• dotnet-legacy-iOS vsdrops gist
• dotnet-legacy-macOS vsdrops gist
• dotnet-legacy-tvOS vsdrops gist
• dotnet-legacy-MacCatalyst vsdrops gist

View dotnet iOS-MacCatalayst API diff

• dotnet-macCatiOS vsdrops gist

GitHub pages

Results can be found in the following github pages (it might take some time to publish):

• Test results
• API diff
• API & Generator diff

Test results

1 tests failed, 131 tests passed.

Failed tests

• monotouch-test/Mac Catalyst [dotnet]/Debug [dotnet]: Failed (Tests run: 2703 Passed: 2500 Inconclusive: 35 Failed: 3 Ignored: 200)

Pipeline on Agent XAMBOT-1100.BigSur'
Merge c47f4bd into 560d777

[spouliot]

👍

[chamons]

Test failure was good old https://github.com/xamarin/maccore/issues/2443

[rolfbjarne]

/sudo backport release/6.0.1xx-preview10

[vs-mobiletools-engineering-service2]

Backport Job to branch release/6.0.1xx-preview10 Created! The magic is happening here

[vs-mobiletools-engineering-service2]

Hooray! Backport succeeded! Please see https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=5367047 for more details.