Add architecture to hash sandbox dir

[microtorus]

This patch allows for 32-bit and 64-bit concurrent builds.

This ensures that dependencies built for different architectures will not get mixed into the same dist-sandbox directory thus allowing for x86 and x86_64 builds in the same working space and even concurrently.

[23Skidoo]

Instead of just $arch, please use $arch-$os-$compiler, like we do elsewhere. Instead of just hashing it, please change the directory to dist/dist-$HASH/$arch-$os-$compiler (aside: we should probably be using a platform-specific directory separator here instead of a slash).

[BardurArantsson]

@ezyang Is this relevant after your changes to "pkgid", etc?

If yes, then why aren't we merging this?

[ezyang]

This looks orthogonal, because it is related to sandbox directory selection which is not based off of a computed component ID. Which mean it should be relevant.

[23Skidoo]

why aren't we merging this?

I guess because GitHub doesn't send notifications when the submitter updates the PR by pushing additional commits. I'll postpone this until after 1.24 is branched because I think there's some potential for breakage.

[BardurArantsson]

Ugh. Another "process" thing forced upon us by GitHub :(

(Good work, btw, getting a release together!)

[phadej]

Sandbox is deprecated.