Context: 4b33a6229c
Remove `tools/xabuild` completely. It is no longer required; use
`dotnet-local.*` instead (4b33a622).
Additionally, remove unneeded pipelines. `build.groovy` and
`azure-pipelines-oss.yaml` (among others) haven't been executed in
*years*; there is no need to keep these files around.
Context: https://docs.microsoft.com/visualstudio/msbuild/customize-your-build?view=vs-2019#customize-the-solution-build
@grendello was hitting a problem building Xamarin.Android on Linux,
every project would fail saying `PackDotNet` does not exist:
$ make pack-dotnet
...
java-runtime.csproj : error MSB4057: The target "PackDotNet" does not exist in the project.
Reading the docs for `Before.*.sln.targets`:
> When MSBuild builds a solution file, it first translates it
> internally into a project file and then builds that. The generated
> project file imports `before.{solutionname}.sln.targets` before
> defining any targets...
`before.` is all lowercase.
Renaming the file to use `before` and not `Before` fixes the build
on Linux.
Marek Habersack
Jonathan Peppers