Support musl-libc based linux RIDs

[eerhardt]

• Add linux-musl RID
• Set alpine's parent to linux-musl
• Add alpine.3.7 to the graph
• Fix up android to inherit from unix while we are here

Fixes https://github.com/dotnet/core-setup/issues/3817

QUESTION: Is linux-musl the correct name for this RID? Do we like the order of the two words? Is using a hyphen to separate them acceptable?

/cc @Petermarcu

[Petermarcu]

lgtm

[janvorli]

Is musl-linux the correct name for this RID? Do we like the order of the two words? Is using a hyphen to separate them acceptable?

This name format makes sense, I only wonder if parsing of RID that we may have at various places would work correctly without changes.

[danmoseley]

@weshaggard for question about RID parsing.

[eerhardt]

test Linux x64 Release Build
test OSX x64 Debug Build

Both System.Net.HttpListener test failures

[weshaggard]

This name format makes sense, I only wonder if parsing of RID that we may have at various places would work correctly without changes.

It should work as far as I'm aware. @steveharter are you aware of anything in the host parsing code that wouldn't handle this naming convention?

[4creators]

IMO as linux is more general term and musl is just a C runtime linux-musl could be better.

[steveharter]

@steveharter are you aware of anything in the host parsing code that wouldn't handle this naming convention?

I am not aware of any parsing code like that. The host really depends on the "fallback graph" in NETCoreApp's runtimeconfig.json to define the list of RIDs and their fallback RIDs.

[eerhardt]

@4creators - we had the opposite opinion from @kasper3 on https://github.com/dotnet/core-setup/issues/3817#issuecomment-376773300.

[eerhardt]

I've renamed the RID to linux-musl. I agree it makes sense to have the more general term first.

[eerhardt]

I've updated linux-musl's parent to be linux based on this discussion: https://github.com/dotnet/core-setup/issues/3817#issuecomment-377328964

[eerhardt]

Can someone review this? I'd like to get it in for ZBB tomorrow.