Bug#862360: llvm-toolchain-3.8: Fix R_AARCH64_MOVW_UABS_G3 relocation

[Graham Inggs]

Control: severity -1 serious
Control: block 861484 by -1

Justification: fails to build from source (but built successfully in the past)

Thanks Edmund!

Builds of llvm-toolchain-3.8 itself have also been failing recently:

https://buildd.debian.org/status/fetch.php?pkg=llvm-toolchain-3.8&arch=arm64&ver=1%3A3.8.1-23&stamp=1493164435&raw=0
https://buildd.debian.org/status/fetch.php?pkg=llvm-toolchain-3.8&arch=arm64&ver=1%3A3.8.1-19%7Eexp4&stamp=1491776717&raw=0
https://buildd.debian.org/status/fetch.php?pkg=llvm-toolchain-3.8&arch=arm64&ver=1%3A3.8.1-19%7Eexp2&stamp=1490502613&raw=0

Also only with kernel >= 3.9 and also on arm-arm-04 and arm-conova-01
https://buildd.debian.org/status/logs.php?pkg=llvm-toolchain-3.8&arch=arm64