* Bump VSMac to 8.1.0.2742 to fix msbuild issues
This is required to get the support for the msbuild `ToolsVersion`
change from `15.0` to `Current`.
* [tests][msbuild] Fix Binding resources test with updated msbuild
Test failure with updated msbuild and vsmac 8.1:
```
Xamarin.iOS.Tasks.NativeReferencesNoEmbedding("iPhone").ShouldNotUnnecessarilyRebuildBindingProject(True)
Binding project build did not create package?
Expected: True
But was: False
at Xamarin.iOS.Tasks.NativeReferencesNoEmbedding.ShouldNotUnnecessarilyRebuildBindingProject (System.Boolean framework) [0x000a0] in <74b8f7d8a53e40109916d305bb4d7403>:0
at (wrapper managed-to-native) System.Reflection.RuntimeMethodInfo.InternalInvoke(System.Reflection.RuntimeMethodInfo,object,object[],System.Exception&)
at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo cul
ture) [0x0006a] in <0519fa732e8845b6a809ce9180f541db>:0
```
The test builds the project multiple times. Before the 3rd build, the project
file's timestamp is updated and expects that the binding package will be
rebuilt. But it is not, because the target `_CreateBindingResourcePackage`
doesn't depend on that project file. So, add that to the target inputs.
* [nuget] Use xibuild to run nuget
Fix errors seen during `nuget restore` for tests:
```
Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/xammac_tests/xammac_tests.csproj(213,3): error MSB4024: The imported project file "/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Mac/Xamarin.Mac.CSharp.targets" could not be loaded. Could not find file "/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Mac/Xamarin.Mac.CSharp.targets"
```
* xibuild: New wrapper tool to run msbuild or managed executables
MSBuild supports fallback paths for projects imported using
`$(MSBuildExtensionsPath)`, but these must be specified explicitly in
the app.config of the main executable. There was a PR to allow use of
properties for this in the app.config, but that was not accepted
upstream.
This is required for being able to:
1. build projects with msbuild against the in-tree XI/XM build output
2. and to run nunit tests against the same.
For this we introduce a new tool, `xibuild`, based on XA's `xabuild`.
This supports the fallback paths to be specified via the environment variable
`MSBuildExtensionsPathFallbackPathsOverride`[1].
It essentially operates in 3 modes:
1. `xibuild -c /path/to/foo.exe`
Generates /path/to/foo.exe.config with the fallback paths inserted into that.
2. `xibuild -- /v:diag /path/to/project.csproj`
Runs msbuild with the arguments after `--` with a custom app.config based on
`MSBuild.dll.config`, with the fallback paths correctly inserted.
This is in a temporary file and the original config file is not touched.
3. `xibuild -t -- /path/to/managed_tool.exe args`
Generates `/path/to/managed_tool.exe.config` based on `MSBuild.dll.config` with
the fallback paths inserted, and runs `managed_tool.exe` with the arguments.
The default is to overwrite the config file.
But there is also a switch to merge it with an existing config file.
--
1. Value of the environment variable $MSBuildExtensionsPathFallbackPathsOverride
is prepended to any existing list of search paths in `MSBuild.dll.config`, IOW,
it takes precedence. So, the order of lookup becomes:
- Value of the property `$(MSBuildExtensionsPath)`
- Value of the environment variable `$MSBuildExtensionsPathFallbackPathsOverride`
- /Library/Frameworks/Mono.framework/External/xbuild on macOS
* Integrate use of `xibuild` with the tests
Update all uses of `msbuild` and invocations of tools like nunit that
might depend on using the in-tree builds to use `xibuild`.
* xibuild: Move help descriptions to OptionSet itself.
- And map xbuild properties to msbuild ones for fallback paths
`XBUILD_FRAMEWORK_FOLDERS_PATH -> TargetFrameworkFallbackSearchPaths`
`MSBuildExtensionsPath -> MSBuildExtensionsPathFallbackPathsOverride`
Note:
Earlier with xbuild, the order of lookup for (example)
`MSBuildExtensionsPath` was:
1. The value of $(MSBuildExtensionsPath), which we were setting to
the in-tree path
2. /Library/Frameworks/Mono.framework/External/xbuild on osx
3. $prefix/lib/mono/xbuild (default location)
And with the above changes, it will be:
1. The value of $(MSBuildExtensionsPath), which we are no longer
setting, so the default path : $prefix/lib/mono/xbuild
2. The in-tree path, via $(MSBuildExtensionsPathFallbackPathsOverride)
3. /Library/Frameworks/Mono.framework/External/xbuild on osx
Since, XI/XM targets are used via fallback path
`/Library/Frameworks/Mono.framework/External/xbuild`, the default
location doesn't matter. And the order of the remaining two remains the
same.
The same thing applies to the target frameworks also.
* [tests] Convert mmp tests to a standard NUnit test library.
* [xharness] Add support for restoring nugets before building projects.
And restore nugets for tests-mac.sln before building mac test projects.