My thought is that we should hold of on merging toolchain changes unless they're actually needed to fix an error. It's a fair amount of work to update things on the builders, so I'd prefer to only do it a couple times a year instead of whenever a toolchain change goes in.
This is in no way unappreciative of everyone's work to keep the toolchains up-to-date, It would just be easier to maintain if we merged toolchain changes at planned times - after we do releases, for example.
Regarding the failure on Smaug, i think it was actually a change that went into the tree AFTER the last toolchain update.
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