[release/3.0] Don't use baseline assembly versions for RID-agnostic packages

[wtgodbe]

In all CI builds except Windows x64, we set OnlyPackPlatformSpecificPackages=true: https://github.com/aspnet/AspNetCore/blob/e6af4bfe7e022e2c3b32c583b280965041c3d15c/.azure/pipelines/ci.yml#L254-L261

This makes us decide that all libraries without RuntimeIdentifiers are not packable: https://github.com/aspnet/AspNetCore/blob/1ff3e7b21ea5270b832a6e05c74b1b5f67d4cfb0/Directory.Build.targets#L5

Then later, we say that everything that is not packable, is not part of "this patch" (if we're doing a patch build): https://github.com/aspnet/AspNetCore/blob/1ff3e7b21ea5270b832a6e05c74b1b5f67d4cfb0/Directory.Build.targets#L62-L68

Which causes us to use basline assembly versions:

https://github.com/aspnet/AspNetCore/blob/1ff3e7b21ea5270b832a6e05c74b1b5f67d4cfb0/Directory.Build.targets#L74-L77

We are incorrect to say that these libraries/packages aren't "in this patch" - we're just not building them right now. Moving the condition for OnlyPackPlatformSpecificPackages down in the file should fix the issue. Without this, all of our non-Windows-x64 builds create runtime packs w/ 3.0.0.0 assembly versioned .dll's.

@JunTaoLuo @Pilchie @dagood @dougbu PTAL

[Pilchie]

We commented on this in the team room, but just remarking here. This may be necessary, but is not sufficient to fix the issues we're having, as we think the extern being used should actually be the ref assembly version, not the implementation assembly version.

[dougbu]

If moving this condition does anything, it's not because of $(IsPackageInThisPatch). That property is always true.

[dougbu]

Sorry, "almost-always true".

But, the comment remains confusing and I didn't get what you were trying to do. Best to make $(IsPackageInThisPatch) irrelevant i.e. remove the https://github.com/aspnet/AspNetCore/pull/17969/files#diff-56f8482aeb786dd105fbf93dedf2615fR78-R94 block. We should never use baseline versions except to confirm dependencies remain unchanged patch-to-patch. Every release is now complete or nearly so; the only optional shipping bits are the targeting packs.

[wtgodbe]

We should never use baseline versions

That was my initial thought as well, but I was a little nervous about not 100% understanding the implications. It now looks like we won't reset January for this, so I have more time to get this right.

[dougbu]

@wtgodbe any luck w/ alternative fixes?

[jamshedd]

Approved for Feb for 3.1.2.

[analogrelay]

@wtgodbe can you retarget this PR to 3.1?

[wtgodbe]

Closing in favor of #17970, which targets 3.1