Cherry-pick swift-testing Linux availability fix to release/6.4.x - #170

Cherry-pick swift-testing Linux availability fix to release/6.4.x#170

heckj merged 1 commit into

swiftlang:release/6.4.xswiftlang/docs:release/6.4.xfrom

heckj:swift-testing-availability-6.4.xheckj/docs:swift-testing-availability-6.4.xCopy head branch name to clipboard