FYI: recommend disabling gold/LTO for aarch64

[Dan Albert]

https://sourceware.org/bugzilla/show_bug.cgi?id=21491

tl;dr: There's a bug in a workaround for some aarch64 errata in ld.gold. This problem is exacerbated by LTO, but can theoretically be triggered even without LTO. Until a fix for this is made to gold (and we get that fix into the NDK), it is not wise to build aarch64 code with gold, and especially not with LTO.

Note that this affects the linker, not the compiler. Both GCC and Clang are affected.

ld.gold is not the default for aarch64 for either toolchain, so unless you've manually added `-fuse-ld=gold` to your build, you are not affected.

This does not affect other architectures. Only aarch64 code is affected.