QuRT: Changes to enable qurt target to build

QuRT doesn't support unlink and does not provide getpid().
The DSPAL layer provides access to usleep so an implementation is
no longer needed.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/systemcmds/param/param.c

@@ -213,7 +213,9 @@ do_save(const char *param_file_name)
 	close(fd);
 
 	if (result < 0) {
+#ifndef __PX4_QURT
 		(void)unlink(param_file_name);
+#endif
 		warnx("error exporting to '%s'", param_file_name);
 		return 1;
 	}