Switch klog buffer to ubyte array to move it to bss section

src/hulk/klog.d

@@ -19,7 +19,7 @@ struct klog
     private enum size_t KLOG_SIZE = 1u << KLOG_SIZE_LOG;
 
     /** Kernel log buffer. */
-    private static __gshared align(4096) char[KLOG_SIZE] klog_buffer;
+    private static __gshared align(4096) ubyte[KLOG_SIZE] klog_buffer;
 
     /** Write index in the kernel log buffer. */
     private static __gshared size_t klog_index;