Cast data buffer to char * for Windows

Author: emmatyping

Include/internal/pycore_blocks_output_buffer.h

@@ -222,7 +222,8 @@ _BlocksOutputBuffer_Grow(_BlocksOutputBuffer *buffer,
     buffer->allocated += block_size;
     buffer->num_blocks += 1;
 
-    *next_out = PyBytesWriter_GetData(buffer->writer) + current_size;
+    char* data = PyBytesWriter_GetData(buffer->writer);
+    *next_out = data + current_size;
     return block_size;
 }