Fix undefined behavior in shape.c

	Under strict aliasing, writing to the memory location of a different
	type is not allowed and will result in undefined behavior. This was
	happening in shape.c due to `rb_id_table_lookup` writing to the memory
	location of `VALUE *` that was casted from a `rb_shape_t **`.

	This was causing test failures when compiled with LTO.

	Fixes [Bug #19248]

Co-Authored-By: Alan Wu <alanwu@ruby-lang.org>
	---
	 shape.c | 13 +++++++++++--
	 1 file changed, 11 insertions(+), 2 deletions(-)