Merge pull request #6453 from lat9nq/libusb-fix-msvc

externals: Don't set FOUND or VERSION on LIBUSB

externals/libusb/CMakeLists.txt

-set(LIBUSB_FOUND ON CACHE BOOL "libusb is present" FORCE)
-set(LIBUSB_VERSION "1.0.24" CACHE STRING "libusb version string" FORCE)
-
 if (MINGW OR (${CMAKE_SYSTEM_NAME} MATCHES "Linux"))
+    set(LIBUSB_FOUND ON CACHE BOOL "libusb is present" FORCE)
+    set(LIBUSB_VERSION "1.0.24" CACHE STRING "libusb version string" FORCE)
+
     # GNU toolchains for some reason doesn't work with the later half of this CMakeLists after
     # updating to 1.0.24, so we do it the old-fashioned way for now.