Regular LLVM test builds in Debian and porterboxes

Hi!

During one of the recent reviews, the concern was raised that there might not be
enough (build-)testing of the non-mainstream architecture backends available so
that these ports may start to bit rot faster [1].

I would therefore like to raise awareness about the fact that Debian is regularly
building new snapshot releases, both of the current SVN trunk [2] as well as the
of the 6.0 [3] and 7 [4] branches.

So, if anyone is wondering whether LLVM currently builds on any of its supported
architectures, just have a look at the builds logs. Those can be viewed by navigating
to buildd.debian.org, then searching for "llvm-toolchain-snapshot", for example.
Branch releases are called "llvm-toolchain-6.0" and "llvm-toolchain-7" respectively.

The "Status" column quickly tells you whether LLVM+Clang build on a given architecture
and clicking either "Installed" or "Build-Attempted" allows one to view the latest
build log. Previous build logs can be inspected by clicking "old" in the "Logs"
column.

Furthermore, Debian has plenty of official and unofficial porterboxes for most
architectures on which accounts can be created upon request. For example, if
someone needs access to a SPARC machine to test a certain patch or debug a
problem, we can create an account on a rather fast SPARC-T5.

Just let me know if you need such an account or if you have any architecture-
specific questions. Support for Debian's non-mainstream architectures (called
"Debian Ports", i.e. anything in the lower, grayed out section of the build
log views) can be obtained by joining the #debian-ports IRC channel on OFTC
network. Furthermore, it's rather simple to create an emulated build environment
with the help of qemu-user, for example for m68k [5].

I hope this helps reducing the concern regarding the testing and maintenance
of the less common LLVM backends a bit!

Thanks,
Adrian