base: Add support for unix domain sockets in ListenSocket.

Change-Id: I6a5fa2cd3e4b567829203bf9d61ad2b55c259697
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/69164
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jui-min Lee <fcrh@google.com>

src/base/socket.test.cc

@@ -207,5 +207,10 @@ TEST(SocketTest, RelistenWithDifferentInstanceOnSamePort)
 TEST(SocketTest, AcceptError)
 {
     MockListenSocket listen_socket(-1);
-    EXPECT_EQ(-1, listen_socket.accept());
+    EXPECT_ANY_THROW(listen_socket.accept());
+    std::string expected =
+        "panic: panic condition sfd == -1 occurred: mock: Failed to accept "
+        "connection: Bad file descriptor\n";
+    std::string actual = gtestLogOutput.str();
+    EXPECT_EQ(expected, actual);
 }