[release/7.0] Fix netfx build for S.S.C.Xml nuget package #78734
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Backport of #78665 to release/7.0
/cc @bartonjs
Customer Impact
Customers upgrading NuGet package references from 6.0.x to 7.0.0 find that the System.Security.Cryptography.Xml and System.Threading.AccessControl packages no longer work on .NET Framework, generally manifesting as a TypeLoadException when used by an intermediate library built targeting .NET Standard 2.0
Testing
Built the release/7.0 branch with this change applied, extracted the
lib/net462DLL for each package, and verified all of the typeforwards are present in the updated versions.Risk
Low.
IMPORTANT: Is this backport for a servicing release? If so and this change touches code that ships in a NuGet package, please make certain that you have added any necessary package authoring and gotten it explicitly reviewed.