PLT entries are PseudoFunctions, and are not disassembled or emitted.
For BTI, we need to check the first MCInst of PLT entries, to see
if indirectly calling them is safe or not.
This patch disassembles PLTs for binaries using BTI, while not changing
the behaviour for binaries without BTI.
The PLTs are only disassembled, not emitted.
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Co-authored-by: Paschalis Mpeis <paschalis.mpeis@arm.com>