[llvm] [Github][libc] Add qemu-system-hexagon to the libc container (PR #219433)

[Brian Cain via llvm-commits]

androm3da wrote:

> > Are there plans to upstream the Hexagon specific patches from the fork into upstream QEMU? Having to build from source from a fork is a bit annoying.

Is it more convenient to download a binary tarball?  If you're using x86_64 ubuntu hosts, then the prebuilt binaries we provide built from this fork might suffice until this content is available upstream.

> plans to upstream Hexagon patches? yes. when? I can't say @androm3da any idea?
> 
> building from source isn't ideal but I think we will have to do this for now

Yes, upstreaming is ongoing.  It's probably best to focus on what specific feature set is required in order to predict when it'll be available upstream.  Since this PR appears to depend on semihosting, I'll assume that it's at least that feature, which is [currently under review](https://lore.kernel.org/qemu-devel/cover.1787586642.git.matheus.bernardino@oss.qualcomm.com/).  I'm pretty confident it'll appear in the 11.2 release.  You might expect that it'll be some time after that before it appears in your-favorite-linux-distro.  What other QEMU features are required by this libc port?

Also: from what I can tell #217528 focuses on baremetal - but if you focused on linux support initially, then you could cover the common elements of libc's hexagon support using the linux userspace emulator.  This could save you the need to build or download QEMU.

https://github.com/llvm/llvm-project/pull/219433