ports/unix: Fix "‘signal_sco_can_send_now’ defined but not used".

Added a "ports/unix/btstack_config.h" for a workaround:
If "MICROPY_BLUETOOTH_BTSTACK_USB" is set and "ENABLE_SCO_OVER_HCI"
is not defined there is a compiler error:
    ../../lib/btstack/platform/libusb/hci_transport_h2_libusb.c:1354:13:
    error: ‘signal_sco_can_send_now’ defined but not used
Because the problem is in an external code a workaround is done by
defining MICROPY_BLUETOOTH_BTSTACK_USB in the added "btstack_config.h".

The "ports/unix/Makefile" has been changed so that the "btstack_config.h"
will be included.

Signed-off-by: Yasmin Bosch <development@yasmin-bosch.de>

ports/unix/Makefile

@@ -52,6 +52,12 @@ endif
 endif
 endif
 
+# Set the file that will be included by "extmod/btstack/btstack_config.h"
+# 
+# The original file "extmod/btstack/btstack_config_common.h"
+# will be included by it. 
+MICROPY_BLUETOOTH_BTSTACK_CONFIG_FILE ?= '"ports/unix/btstack_config.h"'
+
 # include py core make definitions
 include $(TOP)/py/py.mk
 include $(TOP)/extmod/extmod.mk

ports/unix/btstack_config.h

@@ -0,0 +1,23 @@
+#ifndef MICROPY_INCLUDED_PORTS_UNIX_BTSTACK_CONFIG_H
+#define MICROPY_INCLUDED_PORTS_UNIX_BTSTACK_CONFIG_H
+
+
+#include "extmod/btstack/btstack_config_common.h"
+
+#ifdef MICROPY_BLUETOOTH_BTSTACK_USB
+#if MICROPY_BLUETOOTH_BTSTACK_USB
+
+// Workaround:
+//
+// If ENABLE_SCO_OVER_HCI is not defined there is a compiler error:
+//
+// ../../lib/btstack/platform/libusb/hci_transport_h2_libusb.c:1354:13:
+// error: ‘signal_sco_can_send_now’ defined but not used
+//
+// Because the problem is in an external code this workaround is done.
+#define ENABLE_SCO_OVER_HCI
+
+#endif
+#endif
+
+#endif // MICROPY_INCLUDED_PORTS_UNIX_BTSTACK_CONFIG_H