export data to build/sync/data

lib/device.c

@@ -1,6 +1,7 @@
 #include "device.h"
 #include "track.h"
 #include <stdio.h>
+#include <fcntl.h>
 #include <math.h>
 #include <assert.h>
 #include <string.h>
@@ -264,6 +265,14 @@ static int get_track_data(struct sync_device *d, struct sync_track *t)
 static int save_track(const struct sync_track *t, const char *path)
 {
 	int i;
+
+	int cwd = open(".", O_RDONLY);
+	if (!cwd)
+		return -1;
+
+	if (!chdir("build/sync"))
+		return -1;
+
 	FILE *fp = fopen(path, "wb");
 	if (!fp)
 		return -1;
@@ -277,6 +286,9 @@ static int save_track(const struct sync_track *t, const char *path)
 	}
 
 	fclose(fp);
+
+	if (!fchdir(cwd))
+		return -1;
 	return 0;
 }