* [tests] Move linker tests to match introspection directory layout.
Move linker tests to match introspectio directory layout: tests/linker/ios and
tests/linker/mac instead of tests/linker-ios and tests/linker-mac.
This creates a logical place for shared linker files (tests/linker).
* [tests] Fix path to GuiUnit_NET_4_5.csproj in sln as well.
This is the path used to find referenced projects when building Classic.
Fixes this build problem:
warning: Referenced project 'GuiUnit_NET_4_5' not found in the solution.
/Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/common/mac/MacTestMain.cs(11,7) : error CS0246: The type or namespace name `GuiUnit' could not be found. Are you missing an assembly reference?
/Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/common/mac/MacTestMain.cs(64,42) : error CS0246: The type or namespace name `IMainLoopIntegration' could not be found. Are you missing an assembly reference?
/Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/common/mac/MacTestMain.cs(75,34) : error CS0246: The type or namespace name `InvokerHelper' could not be found. Are you missing an assembly reference?
Rolf Bjarne Kvinge