Report a compile err

[Hongyu Xie]

source code:
  https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
base:
  ae0c77e1bc6963c67c6c09e8c72959fcb1ed8d5f
config tested:
  x86_64_defconfig
  defconfig(arm64)
toolchain:
  gcc version 10.4.0 (Ubuntu 10.4.0-4ubuntu1~22.04)
cross compile toolchain:
  gcc version 10.4.0 (Ubuntu 10.4.0-4ubuntu1~22.04)

reproduce compile err:
  CONFIG_WERROR=y && CONFIG_PRINTK=n && CONFIG_UBSAN_ALIGNMENT=y &&
  CONFIG_UBSAN_SANITIZE_ALL=y

compile err log:
kernel/printk/printk.c: In function ‘console_flush_all’:
kernel/printk/printk.c:2845:17: error: array subscript 0 is outside array
bounds of ‘char[0]’ [-Werror=array-bounds]
 2845 |  char *outbuf = &pbufs.outbuf[0];
      |                 ^~~~~~~~~~~~~~~~
In file included from kernel/printk/printk.c:61:
kernel/printk/internal.h:87:7: note: while referencing ‘outbuf’
   87 |  char outbuf[PRINTK_MESSAGE_MAX];
      |       ^~~~~~
kernel/printk/printk.c:2842:31: note: defined here ‘pbufs’
 2842 |  static struct printk_buffers pbufs;
      |                               ^~~~~

I applied the way 5a41237ad1d4 in mainline did for gcc 10, problem goes
away. I'm guessing this is a gcc bug.