Work around Foundation revert (#813)

Motivation Foundation has reverted several of the changes of behaviour in the URL type, leaving 6.0 and 6.1 with a different behaviour on non-Apple platforms than all other versions. We should tolerate that. Modifications Update the tests to understand the difference. Result Tests pass

Author: Lukasa

Tests/AsyncHTTPClientTests/HTTPClientTests.swift

@@ -46,7 +46,7 @@ final class HTTPClientTests: XCTestCaseHTTPClientTestsBaseClass {
 
  let request3 = try Request(url: "unix:///tmp/file")
  XCTAssertEqual(request3.host, "")
- #if os(Linux) && compiler(>=6.0)
+ #if os(Linux) && compiler(>=6.0) && compiler(<6.2)
  XCTAssertEqual(request3.url.host, "")
  #else
  XCTAssertNil(request3.url.host)