Progress bar meaningless on Linux machines with lots of write cache

[baconwaifu]

The progress bar for inject_{cd,dvd} is meaningless on linux systems with large write caches, due to the progress bar only counting what's been commited to writeback, rather than what's actually been written to disk. this leads to a quick "progress" meter, and then the program deadlocking for 5 minutes while it actually gets written out to disk.

A solution is the O_DSYNC flag, which causes write to block until the data hits disk, thus allowing the progress bar to be much more accurate (and not cause the program to lock up for 5 minutes when it calls sync() near the end...)
Simply patching osal_open_device_for_writing to always use O_DSYNC on unix(-likes) appears to work fine, since writing to files either A: goes through a different open call, or B: is being written to a drive that's significantly faster than the source, meaning that it doesn't affect performance noticeably.

Patch:

--- a/osal_unix.c
+++ b/osal_unix.c
@@ -96,7 +96,7 @@ int /* OSAL_OK, OSAL_ERR */
 osal_open_device_for_writing (const char *device_name,
                              osal_handle_t *handle)
 {
-  handle->desc = open (device_name, O_RDWR | O_LARGEFILE, S_IRUSR | S_IWUSR);
+  handle->desc = open (device_name, O_RDWR | O_LARGEFILE | O_DSYNC, S_IRUSR | S_IWUSR);
   return (handle->desc == -1 ? OSAL_ERR : OSAL_OK);
 }