Bug#919626: Emits NEON code on armv7a due to wrong CPU detection

[M. Zhou]

Package: llvm-6.0-dev
Version: 1:6.0.1-9.2
X-Debbugs-CC: ginggs at debian.org

Dear LLVM maintainers,

Recently Julia FTBFS on armhf due to SIGILL from NEON instruction.
(ginggs digged into the SIGILL and confirmed it's due to NEON)
However, julia is supposed to compile multiple code branches where
one of them involves no NEON instruction. Emulation based on QEMU's
cortex-a7 CPU proves this point.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=919183

Neither Debian's LLVM, nor Julia's patched LLVM, has fixed this issue.

The incorrect CPU detection can be reproduced on abel, LLVM
also emits NEON code to abel's CPU.