message: Add a sanity check to the domain socket tests.
  rdar://problem/52062631
diff: @@ -93,6 +93,8 @@ TEST_F(SocketTest, DomainListenConnectAccept) {
  std::error_code EC = llvm::sys::fs::createUniqueDirectory("DomainListenConnectAccept", Path);
  ASSERT_FALSE(EC);
  llvm::sys::path::append(Path, "test");
  + // If this fails, $TMPDIR is too long to hold a domain socket.
  + EXPECT_LE(Path.size(), 107u);
  std::unique_ptr<DomainSocket> socket_a_up;
  std::unique_ptr<DomainSocket> socket_b_up;
  @@ -194,6 +196,8 @@ TEST_F(SocketTest, DomainGetConnectURI) {
  llvm::sys::fs::createUniqueDirectory("DomainListenConnectAccept", domain_path);
  ASSERT_FALSE(EC);
  llvm::sys::path::append(domain_path, "test");
  + // If this fails, $TMPDIR is too long to hold a domain socket.
  + EXPECT_LE(domain_path.size(), 107u);
  std::unique_ptr<DomainSocket> socket_a_up;
  std::unique_ptr<DomainSocket> socket_b_up;
  