Fix some strict prototype warnings;

src/core/os.h

@@ -160,7 +160,7 @@ void os_open_console(void);
 double os_get_time(void);
 void os_sleep(double seconds);
 void os_request_permission(os_permission permission);
-const char* os_get_clipboard_text();
+const char* os_get_clipboard_text(void);
 void os_set_clipboard_text(const char* text);
 
 void* os_vm_init(size_t size);

src/core/os_android.c

@@ -269,7 +269,7 @@ void os_request_permission(os_permission permission) {
   }
 }
 
-const char* os_get_clipboard_text() {
+const char* os_get_clipboard_text(void) {
   return NULL;
 }
 

src/core/os_wasm.c

@@ -246,7 +246,7 @@ void os_request_permission(os_permission permission) {
   //
 }
 
-const char* os_get_clipboard_text() {
+const char* os_get_clipboard_text(void) {
   return NULL;
 }
 

src/modules/graphics/graphics.c

@@ -622,7 +622,7 @@ static BufferView getBuffer(gpu_buffer_type type, uint32_t size, size_t align);
 static int u64cmp(const void* a, const void* b);
 static uint32_t lcm(uint32_t a, uint32_t b);
 static void beginFrame(void);
-static void flushTransfers();
+static void flushTransfers(void);
 static void processReadbacks(void);
 static gpu_pass* getPass(Canvas* canvas);
 static size_t getLayout(gpu_slot* slots, uint32_t count);
@@ -7389,7 +7389,7 @@ static void beginFrame(void) {
 // restored, which is pretty gross, but we don't want to invalidate temp memory (currently this is
 // only a problem for Font: when the font's atlas gets destroyed, it could invalidate the temp
 // memory used by Font:getLines and Pass:text).
-static void flushTransfers() {
+static void flushTransfers(void) {
   if (state.active) {
     size_t cursor = state.allocator.cursor;
     lovrGraphicsSubmit(NULL, 0);