Skip test on big-endian architectures

Due to the memory layout on BE architectures, the address would be
`0x2a00000000` instead of `0x2a` on little-endian architectures.

Fix #79571: FFI: var_dumping unions may segfault

We must not attempt to access arbitrary union members when retrieving
debug info, because that may not be valid. Therefore we do no long

Fix #79571: FFI: var_dumping unions may segfault

We must not attempt to access arbitrary union members when retrieving
debug info, because that may not be valid. Therefore we do no longer
dereference pointer types inside of unions, but report their address as
string in `%p` format instead.

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