Review llvm D55878 default to -Wl,--hash-style=gnu

[Ray]

Can someone review this upstream clang change
https://reviews.llvm.org/D55878 for default -Wl,--hash-style option
used on FreeBSD? The current reviewers might be busy at the moment..

MIPS ABI require .dynsym to be s orted in a different way, but other
architectures can benefit from this change (a few hundreds bytes to a
few kilobytes for typical executables).