Run "ninja check" for armv7 bot and don't pretend we run
LNT testsuite for the aarch64 bot.
[zorg] Build all targets on Linaro-maintained bots
... not just AArch64 and ARM. Make an exception for the quick
bots, which build a single target.
[zorg] Add AArch64 SVE vector-length-specific (VLS) bot
At the moment the only SVE-enabled part is building/running testsuite,
and we'll enable 2-stage builds with SVE later.