externals: libusb: Link libusb statically on Linux

Turns out that this is possible. Also addresses my own review comment.

CMakeLists.txt

@@ -430,13 +430,13 @@ if(NOT APPLE AND NOT YUZU_USE_BUNDLED_LIBUSB)
         find_package(LibUSB)
     endif()
 
-    if (NOT LIBUSB_FOUND)
-        message(WARNING "libusb not found, falling back to externals")
-        set(YUZU_USE_BUNDLED_LIBUSB ON)
-    else()
+    if (LIBUSB_FOUND)
         add_library(usb INTERFACE)
         target_include_directories(usb INTERFACE "${LIBUSB_INCLUDE_DIRS}")
         target_link_libraries(usb INTERFACE "${LIBUSB_LIBRARIES}")
+    else()
+        message(WARNING "libusb not found, falling back to externals")
+        set(YUZU_USE_BUNDLED_LIBUSB ON)
     endif()
 endif()