[release/6.0] Don't regress SkipLocalsInit optimization on < 6.0 .NETCoreApp assets

[ViktorHofer]

Customer Impact

netcoreapp3.1 and net5.0 assets which are part of the Microsoft.NETCore.App shared framework and ship inside a package need to keep the SkipLocalsInit optimization to avoid regressing perf. This would happen when referencing one of the 6.0 packages but consuming either the netcoreapp3.1 or net5.0 asset in it. The higher assembly version of the netcoreapp3.1/net5.0 asset would win over the same asset in the shared framework and without this fix, the SkipLocalsInit optimization would be lost.

Testing

Manually tested. Made sure that the optimization is correctly applied to netcoreapp3.1 or net5.0 assets which are part of the shared framework when producing the 6.0 package.

Risk

Low. This impacts 6.0 packages which contain netcoreapp3.1 or net5.0 assets that are part of the shared framework.

Contributes to #54964

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Issue Details

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net5.0 assets which are part of the Microsoft.NETCore.App shared framework and ship inside a package need to keep the SkipLocalsInit optimization to avoid regressing perf. This would happen when referencing a 6.0 package but consuming the net5.0 asset in it. The higher assembly version of the net5.0 asset would win over the same asset in the 5.0 shared framework and without this fix, the SkipLocalsInit optimization would be lost.

Contributes to #54964

Author:	ViktorHofer
Assignees:	ViktorHofer
Labels:	area-Infrastructure-libraries
Milestone:	-

[danmoseley]

Approved to merge into release/6.0 as it's a significant regression. Please verify in a build after it goes in.

[ViktorHofer]

/backport to main