Merge pull request dotnet/corefx#35533 from dotnet/Add-Alpine-3-9
authorMatt Galbraith <MattGal@users.noreply.github.com>
Fri, 22 Feb 2019 22:20:15 +0000 (14:20 -0800)
committerGitHub <noreply@github.com>
Fri, 22 Feb 2019 22:20:15 +0000 (14:20 -0800)
Adding Alpine 3.9 Runs to official

Commit migrated from https://github.com/dotnet/corefx/commit/dc6dfe11752a00136df36b5c62f6b891322068e6


Trivial merge