Fix ssd1306 compilation on avr-gcc 10 (#9267)

drivers/avr/ssd1306.c

@@ -11,6 +11,8 @@
 #    include "sendchar.h"
 #    include "timer.h"
 
+struct CharacterMatrix display;
+
 // Set this to 1 to help diagnose early startup problems
 // when testing power-on with ble.  Turn it off otherwise,
 // as the latency of printing most of the debug info messes

drivers/avr/ssd1306.h

@@ -66,7 +66,7 @@ struct CharacterMatrix {
     bool     dirty;
 };
 
-struct CharacterMatrix display;
+extern struct CharacterMatrix display;
 
 bool iota_gfx_init(void);
 void iota_gfx_task(void);

keyboards/claw44/ssd1306.c

@@ -10,6 +10,8 @@
 #include "sendchar.h"
 #include "timer.h"
 
+struct CharacterMatrix display;
+
 extern const unsigned char font[] PROGMEM;
 
 // Set this to 1 to help diagnose early startup problems

keyboards/claw44/ssd1306.h

@@ -65,7 +65,7 @@ struct CharacterMatrix {
   bool dirty;
 };
 
-struct CharacterMatrix display;
+extern struct CharacterMatrix display;
 
 bool iota_gfx_init(bool rotate);
 void iota_gfx_task(void);

keyboards/comet46/ssd1306.c

@@ -10,6 +10,8 @@
 #include "sendchar.h"
 #include "timer.h"
 
+struct CharacterMatrix display;
+
 extern const unsigned char font[] PROGMEM;
 
 // Set this to 1 to help diagnose early startup problems

keyboards/comet46/ssd1306.h

@@ -65,7 +65,7 @@ struct CharacterMatrix {
   bool dirty;
 };
 
-struct CharacterMatrix display;
+extern struct CharacterMatrix display;
 
 bool iota_gfx_init(bool rotate);
 void iota_gfx_task(void);

keyboards/crkbd/ssd1306.c

@@ -10,6 +10,8 @@
 #include "sendchar.h"
 #include "timer.h"
 
+struct CharacterMatrix display;
+
 extern const unsigned char font[] PROGMEM;
 
 #ifndef OLED_BLANK_CHAR

keyboards/crkbd/ssd1306.h

@@ -65,7 +65,7 @@ struct CharacterMatrix {
   bool dirty;
 };
 
-struct CharacterMatrix display;
+extern struct CharacterMatrix display;
 
 bool iota_gfx_init(bool rotate);
 void iota_gfx_task(void);

keyboards/helix/local_drivers/ssd1306.c

@@ -16,6 +16,8 @@
 #include "sendchar.h"
 #include "timer.h"
 
+struct CharacterMatrix display;
+
 // Set this to 1 to help diagnose early startup problems
 // when testing power-on with ble.  Turn it off otherwise,
 // as the latency of printing most of the debug info messes

keyboards/helix/local_drivers/ssd1306.h

@@ -66,7 +66,7 @@ struct CharacterMatrix {
   bool dirty;
 };
 
-struct CharacterMatrix display;
+extern struct CharacterMatrix display;
 
 bool iota_gfx_init(bool rotate);
 void iota_gfx_task(void);

keyboards/yosino58/ssd1306.c

@@ -10,6 +10,8 @@
 #include "sendchar.h"
 #include "timer.h"
 
+struct CharacterMatrix display;
+
 extern const unsigned char font[] PROGMEM;
 
 // Set this to 1 to help diagnose early startup problems

keyboards/yosino58/ssd1306.h

@@ -70,7 +70,7 @@ struct CharacterMatrix {
   bool dirty;
 };
 
-struct CharacterMatrix display;
+extern struct CharacterMatrix display;
 
 bool iota_gfx_init(bool rotate);
 void iota_gfx_task(void);