Roslyn Incremental compiler issue

[konstantin890]

Describe the bug
Starting a project/building it or entering playmode drops warning when using the Roslyn incremental compiler (v0.0.42) in Unity 2018.2.14f (same with 2018.1+). Even with this warning all the functionality of Mirror seems to be fine

Unable to delete file Library/ScriptAssemblies/Assembly-CSharp.pdb: Sharing violation on path Library/ScriptAssemblies/Assembly-CSharp.pdb UnityEngine.Debug:LogWarning(Object) Mirror.Weaver.Weaver:Weave(String, IEnumerable1, IAssemblyResolver, String, String, String)
Mirror.Weaver.Weaver:WeaveAssemblies(IEnumerable1, IEnumerable1, IAssemblyResolver, String, String, String)
Mirror.Weaver.Program:Process(String, String, String, String[], String[], IAssemblyResolver, Action1, Action1)
Mirror.Weaver.<>c:<.cctor>b__0_0(String, CompilerMessage[])
UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface:TickCompilationPipeline(EditorScriptCompilationOptions, BuildTargetGroup, BuildTarget)`

To Reproduce
Just put Mirror into an empty project with the Roslyn Incremental compiler enabled (2018.1+/0.0.42)
Installation instructions for the compiler: https://goo.gl/6FmREG (first post)

Expected behavior
The warning not to appear

Desktop:

• OS: Windows
• Build target: Standalone
• Unity version: 2018.1+ (not tested in the 2018.3 beta)
• Latest Mirror 495

[paulpach]

This issue is handled fine in Mirror. We handle it and just print the warning, you can ignore the warning

This is a duplicate of #29