ICU-22977 Fix MSVC builds - Forcing target version

[mihnita]

Defined TargetFrameworkVersion, following this doc:
https://learn.microsoft.com/en-us/cpp/build/how-to-modify-the-target-framework-and-platform-toolset?view=msvc-170#target-framework-ccli-project-only

I am not sure if it is the right fix. It worked just fine for so many years.

Will see what the GitHub team says.

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22977
• Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[jira-pull-request-webhook]

Hooray! The files in the branch are the same across the force-push. 😃

~ Your Friendly Jira-GitHub PR Checker Bot

[rp9-next]

Thanks for working on this! I too was looking into some solutions such as retargeting platform version (#3277), but couldn't get it to work without reverting to windows-2019 which made me believe this might be another vm runner update of MSVC issue.

May I ask, how did you get to <TargetFrameworkVersion>10.0</TargetFrameworkVersion> ?

Looking at docs, it seems to be the .NET Framework version the latest of which is .NET 4.8 or (.NET 8 for .NET core). Was this set through visual studio IDE ?

[rp9-next]

Perhaps the arm build is failing due to this change ?

[rp9-next]

.NET 8 for .NET core

My bad, .NET 9 was released a few days ago that gets included in Visual Studio 17.12. Perhaps that's the source of the build failures.
https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core

[mihnita]

@rp9-next
Do you think I should make it 9.0 instead of 10.0?

[mihnita]

Perhaps the arm build is failing due to this change ?

Yes, already fixed (6 hours ago)

[mihnita]

May I ask, how did you get to 10.0 ?

The error pointed me to the right file and line.
I diff-ed the file pre / post update (from a Windows snapshot).

I removed the condition on version and the failure was fixed.
So then I tried to make it pass the test.

I have doubts about 10.0
Maybe should be 9.0. Or maybe v4.8

Was this set through visual studio IDE ?

No, it was "by hand" following this doc:
https://learn.microsoft.com/en-us/cpp/build/how-to-modify-the-target-framework-and-platform-toolset?view=msvc-170#target-framework-ccli-project-only

[markusicu]

adding or removing the signature byte sequence (aka BOM)?

[rp9-next]

I have doubts about 10.0
Maybe should be 9.0. Or maybe v4.8

According to https://learn.microsoft.com/en-us/dotnet/standard/frameworks#latest-versions, 9.0 seems like a valid target version. Perhaps 9.0 (or 8.0 if for some reason it doesn't work).
I think this is better fix (vs #3277) if CI gets green.