Update to allow clean build using Xamarin Studio and Mono Develop

Cross-project references don't seem to work in Xamarin Studio and Mono Develop "Build" on OSX if a trailing "\" is on the end of the OutputPath

Author: fsgit

src/fsharp/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj

@@ -26,7 +26,7 @@
     <OtherFlags>$(OtherFlags) --times</OtherFlags>
     <NoWarn>$(NoWarn);69;65;54;61;75</NoWarn>
     <DebugSymbols>true</DebugSymbols>
-    <OutputPath>..\..\..\bin\$(TargetFrameworkVersion)\</OutputPath>
+    <OutputPath>..\..\..\bin\$(TargetFrameworkVersion)</OutputPath>
     <DocumentationFile>$(OutputPath)$(AssemblyName).xml</DocumentationFile>
     <DefineConstants>$(DefineConstants);CROSS_PLATFORM_COMPILER</DefineConstants>
     <DefineConstants>$(DefineConstants);FX_ATLEAST_45</DefineConstants>
@@ -614,4 +614,4 @@
   <Import Project="$(LkgPath)\FSharp.SRGen.targets" />
   <Import Project="$(LkgPath)\FSharp.PowerPack.targets" />
   <Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$(SolutionDir)\.nuget\NuGet.targets')" />
-</Project>
+</Project>