Linux: Fix building of static binaries with hw device support

This should enable building static binaries on Linux systems where dependencies are already built with -fPIC, such as Ubuntu 18.04.

cmake/FindHIDAPI.cmake

@@ -39,6 +39,20 @@ find_package_handle_standard_args(HIDAPI
 
 if(HIDAPI_FOUND)
   set(HIDAPI_LIBRARIES "${HIDAPI_LIBRARY}")
+  if((STATIC AND UNIX AND NOT APPLE) OR (DEPENDS AND CMAKE_SYSTEM_NAME STREQUAL "Linux"))
+    find_library(LIBUSB-1.0_LIBRARY usb-1.0)
+    find_library(LIBUDEV_LIBRARY udev)
+    if(LIBUSB-1.0_LIBRARY)
+      set(HIDAPI_LIBRARIES "${HIDAPI_LIBRARIES};${LIBUSB-1.0_LIBRARY}")
+      if(LIBUDEV_LIBRARY)
+        set(HIDAPI_LIBRARIES "${HIDAPI_LIBRARIES};${LIBUDEV_LIBRARY}")
+      else()
+        message(WARNING "libudev library not found, binaries may fail to link.")
+      endif()
+    else()
+      message(WARNING "libusb-1.0 library not found, binaries may fail to link.")
+    endif()
+  endif()
 
   set(HIDAPI_INCLUDE_DIRS "${HIDAPI_INCLUDE_DIR}")
 endif()