spa: support: send TID to systemd journal

Knowing which thread posted which log message can
be useful, so send the TID to the systemd journal.

The `TID` field is explicitly listed on
https://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html#TID=

spa/plugins/support/journal.c

@@ -22,6 +22,8 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include "config.h"
+
 #include <stddef.h>
 #include <unistd.h>
 #include <string.h>
@@ -114,6 +116,9 @@ impl_log_logtv(void *object,
 	sd_journal_send_with_location(file_buffer, line_buffer, func,
 				      "MESSAGE=%s", message_buffer,
 				      "PRIORITY=%i", priority,
+#ifdef HAVE_GETTID
+				      "TID=%jd", (intmax_t) gettid(),
+#endif
 				      NULL);
 }
 

spa/plugins/support/meson.build

@@ -61,6 +61,7 @@ if systemd_dep.found()
 
   spa_journal_lib = shared_library('spa-journal',
     spa_journal_sources,
+    include_directories : [ configinc ],
     dependencies : [ spa_dep, systemd_dep ],
     install : true,
     install_dir : spa_plugindir / 'support')