Run CI against Linux-ARMv7 Community CIs

[helje5]

Swift itself now runs against the CI against ARMv7 Debian: Swift Community-Hosted Continuous Integration.
Would be cool if that could also be somehow used to test NIO on ARMv7. If needed I can hook you up with the guy hosting the ARM build farm.

P.S.: Looks like there will also be a CI for ARM "big iron" (w/ ARM64v8): swiftlang/swift-community-hosted-continuous-integration#10 (those 96 cores machines: https://www.packet.net/bare-metal/servers/c1-large-arm/)

[weissi]

CC @tomerd is this something we can do?

[Lukasa]

This is still live: there is a need to test on armv7 for other projects. But we really do need the Swift team to spin something supported.