[test] [support] Use socket()+bind() to create unix sockets portably

Replace the mknod() call with socket() + bind() for creating unix
sockets.  The mknod() method is not portable and does not work
on NetBSD while binding the socket should work on all systems supporting
unix sockets.

Differential Revision: https://reviews.llvm.org/D55576

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@349305 91177308-0d34-0410-b5e6-96231b3b80d8

test/support/filesystem_dynamic_test_helper.py

@@ -1,5 +1,6 @@
 import sys
 import os
+import socket
 import stat
 
 # Ensure that this is being run on a specific platform
@@ -76,8 +77,13 @@ def create_fifo(source):
 
 
 def create_socket(source):
-    mode = 0o600 | stat.S_IFSOCK
-    os.mknod(sanitize(source), mode)
+    sock = socket.socket(socket.AF_UNIX)
+    sanitized_source = sanitize(source)
+    # AF_UNIX sockets may have very limited path length, so split it
+    # into chdir call (with technically unlimited length) followed
+    # by bind() relative to the directory
+    os.chdir(os.path.dirname(sanitized_source))
+    sock.bind(os.path.basename(sanitized_source))
 
 
 if __name__ == '__main__':