Build: Don't add libusb include until after libftdi

This fixes GH-46 and a regression caused by 82954d9 where the project
would fail to build until configured a second time on Unix-y platforms.

LibFTDI adds libusb, so we need to make sure that's included first.

Windows does not use libusb so it does not need the include directory.

CMakeLists.txt

@@ -207,7 +207,6 @@ target_include_directories(icsneocpp
 	PRIVATE
 		${CMAKE_CURRENT_SOURCE_DIR}/include
 		${LIBICSNEO_EXTENSION_INCLUDE_PATHS}
-		${LIBUSB_INCLUDE_DIR}
 )
 set_property(TARGET icsneocpp PROPERTY POSITION_INDEPENDENT_CODE ON)
 target_compile_features(icsneocpp PUBLIC cxx_auto_type cxx_constexpr cxx_lambdas cxx_nullptr cxx_range_for cxx_rvalue_references cxx_sizeof_member cxx_strong_enums)
@@ -225,6 +224,7 @@ if(NOT WIN32)
 	set(FTDIPP OFF CACHE INTERNAL "")
 	set(FTDI_EEPROM OFF CACHE INTERNAL "")
 	add_subdirectory(third-party/libftdi)
+	target_include_directories(icsneocpp PRIVATE ${LIBUSB_INCLUDE_DIR})
 endif(NOT WIN32)
 
 # winpcap