investigate ppc image

[nickdesaulniers]

continued from ClangBuiltLinux/continuous-integration#62

The current image is x86_64 only. Looks like folks are researching how to make these images slightly more portable.

[nathanchance]

Few initial notes:

1. It doesn't seem terribly difficult to have multi-arch containers (https://blog.docker.com/2017/11/multi-arch-all-the-things/), I will need to do further research into how to actually build them (http://cloudgeekz.com/1352/powerpc-docker-images-on-intel.html?)

2. As Joel notes in that pull request, not having access to multi-arch builds of Clang seems like a bigger blocker than the container itself. Mark Rutland's suggestion to have Clang binaries available on kernel.org (comment) seems like a decent way to start getting around this.

3. Getting QEMU up to date upstream would eliminate any need to build any code thus making creating the images more portable (although we could get around that with a cross compiler in the meantime).

[shenki]

2. As Joel notes in that pull request, not having access to multi-arch builds of Clang seems like a bigger blocker than the container itself. Mark Rutland's suggestion to have Clang binaries available on kernel.org (comment) seems like a decent way to start getting around this.

I opened this issue: https://bugs.llvm.org/show_bug.cgi?id=39985

If we're after nightly builds, we need something like that enabled.

If the goal is to test clang with a llvm that works (which misses out on the improvements that clang makes, but does help keep Linux from regressing) we can us the clang packages from Debian experimental:

https://packages.debian.org/experimental/clang-8

That route is attractive as the work would be trivially reusable if someone wanted arm64 packages.

[nickdesaulniers]

@sylvestre might be able to help package clang for PPC hosts for debian!