[arm] Add big-endian version of pcrel fixups for adr instructions

Summary:
In 2e24219, a number of ARM pcrel fixups were resolved at assembly
time, to solve PR44929. This only covered little-endian ARM however, so
add similar fixups for big-endian ARM. Also extend the test case to
cover big-endian ARM.

Reviewers: hans, psmith, MaskRay

Reviewed By: psmith, MaskRay

Subscribers: kristof.beyls, hiraditya, danielkiss, emaste, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79774

(cherry picked from commit fc37352)

Tag 10.0.0

Tag 10.0.0-rc6

Tag 10.0.0-rc5

Tag 10.0.0-rc4

Tag 10.0.0-rc3

Tag 10.0.0-rc2

Tag 10.0.0-rc1

Tag the 11.0.0 version bump.

export.sh: Fetch sources from GitHub instead of SVN

Reviewers: hansw, jdoerfert

Subscribers: sylvestre.ledru, mgorny, hans, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70460

(cherry picked from commit edf6717)