Make --skip-unresolved the default when not running from SDK

[Youssef1313]

Closes #90469

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Issue Details

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Author:	Youssef1313
Assignees:	-
Labels:	area-Tools-ILLink
Milestone:	-

[vitek-karas]

The test failures are real it seems - could you please take a look? It's likely that couple of tests took an unintentional dependency on the setting being false by default. It should be enough to add an explicit --skip-unresolved false to these tests.

[vitek-karas]

@sbomer - what do you think about making this change. Personally I like it - as it makes the tests behave the "expected" way by default. The fact that if something is using the command line directly (even though unsupported) and gets a more predictable behavior is just a nice side effect for me.

[sbomer]

Seems like a good direction to me - we want the command-line to be consistent with the MSBuild behavior. Please also remove this line:

runtime/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets

Line 224 in 1b7263e

<_ExtraTrimmerArgs>--skip-unresolved true $(_ExtraTrimmerArgs)</_ExtraTrimmerArgs>

[sbomer]

A downside of this change is that we will be losing some test coverage of the --skip-unresolved false mode (see #91007 (comment) for a discussion of where this might be useful). cc @mrvoorhe in case you have any concerns.

[sbomer]

Thanks for your contribution @Youssef1313!

[mrvoorhe]

Thanks for the heads up @sbomer. I'm not sure if I'm concerned about test coverage or not. This code has been pretty stable without much in the way of test coverage. If I become concerned about it I can grab our old tests for unresolved stubbing and adapt them to be --skip-unresolved=false tests