Fix a path typo in FindLibUSB.cmake

Author: xlz

examples/protonect/cmake_modules/FindLibUSB.cmake

@@ -16,7 +16,7 @@ ENDIF()
 FIND_PATH(LibUSB_INCLUDE_DIRS
   NAMES libusb.h
   PATHS
-    "${DEPENDS_DIR}/libusb"
+    "${DEPENDS_DIR}/libusb/libusb" # libusb git tree
     "${DEPENDS_DIR}/libusbx"
     ENV LibUSB_ROOT
   PATH_SUFFIXES