Currently our Linux binaries aren't quite as portable as they otherwise could
be. There's two primary reasons for this, and one of them is that the binary is
produced in a relatively recent Linux distribution (Ubuntu 16.04) which means
it has a relatively recent requirement in terms of glibc versions. On
OSX/Windows we can set some flags to rely on older libc implementations, but on
Linux we have to actually build against an older version.
This commit switches the container for the build to CentOS 6 instead of the
default Ubuntu 16.04. The main trick here is also finding a C++11-capable
compiler to compile wabt. Turns out though there's a helpful tutorial for this
at https://edwards.sdsu.edu/research/c11-on-centos-6/ and it was as easy as
installing a few packages.
The second portability concern of our Linux binaries is that they link
dynamically to `libstdc++.so` which isn't always installed on target systems,
or even if it is it may be too old or have a different ABI. This is solved by
statically linking to `libstdc++.a` in the build on Azure by doing a bit of
trickery with libraries and what's available.
After these results the glibc requirements drops from 2.18 (released in 2013)
to 2.6 (released in 2007) and avoids the need for users to have libstdc++.so
installed. We may eventually want to investigate fully-static musl binaries,
but finding a musl compiler for C++ is something I'm not that good at, so I
figure this is probably good enough for now.
* Refactor Azure Pipelines config and tweak releases
* Extract out doc/rustfmt jobs into their own separate builders. Helps
avoiding having to skip tons of steps and can get failing results more
quickly.
* Extract out Rust installation logic to a dedicated template.
* Separate out the build/test job matrices, where one matrix runs tests
and another runs a full build
* Refactor release directory structure to follow a convention where
`foo.tar.gz` extracts to a folder called `foo` and follow unix-like
conventions and copy over the license/readme files into the release
tarballs.
* Swap order of build/test
