[compiler-rt] [scudo] Fix isOwned on MTE devices. (PR #110717)

[Evgenii Stepanov via llvm-commits]

eugenis wrote:

The problem was reading the header in Chunk::isValid. If you check the test for isOwned, the buffer for that is stack allocated, and not guaranteed to have any specific tag.

https://github.com/llvm/llvm-project/pull/110717