[release/5.0-rc2] Exclude .a files from the runtime native files when packaging

[github-actions]

Backport of #41966 to release/5.0-rc2

/cc @vitek-karas

Customer Impact

We're including static lib files (.a) with our native libraries when shipping either shared framework or runtime packs. These files are not used by the runtime in any way, so it's wasted space. This makes both shared framework and probably more importantly any self-contained app bigger.
On linux-x64 these files combined are almost 7MB in size.

Testing

Verified that the files are not packaged into the runtime packages produced by the dotnet/runtime repo build.

Risk

I think it's low - the affected libraries are all internal and we don't document their APIs. At runtime they're only used through PInvoke which doesn't use .a files for anything. The only possible break would be if somebody used the files to link against the native libraries - for which we don't document any APIs and they're considered internal implementation detail.
The affected files are:

libSystem.IO.Compression.Native.a
libSystem.Native.a
libSystem.Net.Http.Native.a
libSystem.Net.Security.Native.a
libSystem.Security.Cryptography.Native.OpenSsl.a

Note that we shipped these in 3.1 both in the shared framework as well as when publishing self-contained apps. So it's not a regression in 5.0 to keep shipping them if we decide to do so.

[Dotnet-GitSync-Bot]

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[jeffschwMSFT]

Approved. We can take this for consideration in RC2

[jeffschwMSFT]

Reconsidered due to the potential breaking nature.

[danmoseley]

Just curious, for context, what is the size of a hello world self contained app, of which this 7MB is a part?

[jeffschwMSFT]

We recently published numbers in our trimming blog entry (https://devblogs.microsoft.com/dotnet/app-trimming-in-net-5/). 7mb is roughly 10%

[jeffschwMSFT]

Moving to .NET 6