dumpcap: Fix pipe read deadlock on Windows

The deadlock would occur if pipe was closed before the requested number
of bytes was read.

Bug: 15695
Change-Id: I1236dd397d3c268dd52233ea78fb58165d0c9398
Reviewed-on: https://code.wireshark.org/review/32907
Reviewed-by: Anders Broman <a.broman58@gmail.com>

dumpcap.c

@@ -1348,6 +1348,12 @@ static void *cap_thread_read(void *arg)
         }
         g_mutex_unlock(pcap_src->cap_pipe_read_mtx);
     }
+    /* Post to queue if we didn't read enough data as the main thread waits for the message */
+    g_mutex_lock(pcap_src->cap_pipe_read_mtx);
+    if (pcap_src->cap_pipe_bytes_read < pcap_src->cap_pipe_bytes_to_read) {
+        g_async_queue_push(pcap_src->cap_pipe_done_q, pcap_src->cap_pipe_buf); /* Any non-NULL value will do */
+    }
+    g_mutex_unlock(pcap_src->cap_pipe_read_mtx);
     return NULL;
 }
 #endif