Add missing include for symlink()

(cherry picked from commit 7671108aa8)

src/internet/spotifyblobdownloader.cpp

@@ -15,8 +15,9 @@
    along with Clementine.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include "config.h"
 #include "spotifyblobdownloader.h"
+
+#include "config.h"
 #include "spotifyservice.h"
 #include "core/logging.h"
 #include "core/network.h"
@@ -32,6 +33,10 @@
   #include <QtCrypto>
 #endif // HAVE_QCA
 
+#ifdef Q_OS_UNIX
+  #include <unistd.h>
+#endif
+
 const char* SpotifyBlobDownloader::kSignatureSuffix = ".sha1";