[lldb/windows] Make "anonymous" pipe names more unique

Using a "random" name for an "anonymous" pipe seems to be the state of
the art on windows (according to stack overflow, new windows versions
may have something better, but it involves calling kernel APIs directly
and generally a lot of dark magic).

The problem with the current method was that is does not produce unique
names if one has two copies of the pipe code in the same process, which
is what happened with llvm#120457 (because liblldb only exposes the public
api, and we've started using the pipe code in lldb-dap as well).

This patch works around the problem by adding the address of the counter
variable to the pipe name.

Replicating the multiple-copies setup in a test would be very difficult,
which is why I'm not adding a test for this scenario.

Author: labath

lldb/source/Host/windows/PipeWindows.cpp

@@ -71,9 +71,8 @@ Status PipeWindows::CreateNew(bool child_process_inherit) {
   // cannot get overlapped i/o on Windows without using a named pipe.  So we
   // synthesize a unique name.
   uint32_t serial = g_pipe_serial.fetch_add(1);
-  std::string pipe_name;
-  llvm::raw_string_ostream pipe_name_stream(pipe_name);
-  pipe_name_stream << "lldb.pipe." << ::GetCurrentProcessId() << "." << serial;
+  std::string pipe_name = llvm::formatv(
+      "lldb.pipe.{0}.{1}.{2}", GetCurrentProcessId(), &g_pipe_serial, serial);
 
   return CreateNew(pipe_name.c_str(), child_process_inherit);
 }