Use static class member instead of global var

Author: sebromero

src/USBStorage.cpp

@@ -6,6 +6,8 @@
 
 #define MAX_TRIES 10
 
+bool USBStorage::usb_available = false;
+
 USBStorage::USBStorage(){
  #if defined(ARDUINO_PORTENTA_C33)
          register_hotplug_callback(DEV_USB,  [](){

src/USBStorage.h

@@ -3,9 +3,6 @@
 #ifndef USBStorage_H
 #define USBStorage_H
 
-
-static bool usb_available = false;
-
 /**
  * Represents a USB storage using the Arduino Unified Storage library.
  */
@@ -84,6 +81,7 @@ class USBStorage : public Arduino_UnifiedStorage {
     bool connected = false;
     unsigned long previousMillis; 
     int interval = 500;
+    static bool usb_available;
 };
 
 #endif