[lld] Remove usage of `%T` in `lld/test` (#126133)
`%T` is not unique and deprecated
[[1](https://llvm.org/docs/CommandGuide/lit.html#substitutions)].
This patch replaces all `%T` in `lld/test` with `%t.dir` (`mkdir` if
necessary)
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Signed-off-by: Peter Rong <PeterRong@meta.com>
