Error: taking address of packed member of ‘struct regcache_rbtree_node’ may result in an unaligned pointer value

Trying to rebuild kernel-4.9 from source, but obtaining the following ERROR message. I’m using Ubuntu 20.04.1 with gcc 9.3

....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c:36:1: error: alignment 1 of ‘struct regcache_rbtree_node’ is less than 8 [-Werror=packed-not-aligned]
   36 | } __attribute__ ((packed));
      | ^
....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c: In function ‘regcache_rbtree_insert’:
....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c:130:15: error: taking address of packed member of ‘struct regcache_rbtree_node’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
  130 |  rb_link_node(&rbnode->node, parent, new);
      |               ^~~~~~~~~~~~~
....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c:131:18: error: taking address of packed member of ‘struct regcache_rbtree_node’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
  131 |  rb_insert_color(&rbnode->node, root);
      |                  ^~~~~~~~~~~~~
....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c: In function ‘regcache_rbtree_exit’:
....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c:243:18: error: taking address of packed member of ‘struct regcache_rbtree_node’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
  243 |   next = rb_next(&rbtree_node->node);
      |                  ^~~~~~~~~~~~~~~~~~
....../kernel-4.9/drivers/base/regmap/regcache-rbtree.c:244:12: error: taking address of packed member of ‘struct regcache_rbtree_node’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
  244 |   rb_erase(&rbtree_node->node, &rbtree_ctx->root);

Any suggestions?

Please use GCC 7.3.1

https://docs.nvidia.com/jetson/l4t/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide%2Fxavier_toolchain.html%23