darwin: Fix Makefile build on macOS 10.11 and older

TARGET_OS_OSX is not defined when building with the clang 8 provided by
Xcode 8.2.1 on 10.11.5 (unless the Xcode project is used).

If it is not defined we'll just assume we have a "OSX" target.

Closes #1097

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>

libusb/os/darwin_usb.c

diff --git a/libusb/os/darwin_usb.c b/libusb/os/darwin_usb.c
index 3b9fd84..5439d06 100644
--- a/libusb/os/darwin_usb.c
+++ b/libusb/os/darwin_usb.c
@@ -2446,7 +2446,7 @@
 
 /* macOS APIs for getting entitlement values */
 
-#if TARGET_OS_OSX
+#if !defined(TARGET_OS_OSX) || TARGET_OS_OSX == 1
 #include <Security/Security.h>
 #else
 typedef struct __SecTask *SecTaskRef;

libusb/version_nano.h

diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index f9d6b03..7fbdfb5 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11714
+#define LIBUSB_NANO 11715