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[ELF] Add support for older Arm Architectures with smaller branch range

Description

[ELF] Add support for older Arm Architectures with smaller branch range

The Thumb BL and BLX instructions on older Arm Architectures such as v5 and
v6 have a constrained encoding J1 and J2 must equal 1, later Architectures
relaxed this restriction allowing J1 and J2 to be used to calculate a larger
immediate.

This patch adds support for the old encoding, it is used when the build
attributes for the input objects only contain older architectures.

Differential Revision: https://reviews.llvm.org/D50076

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