Couchbase.Lite.Unity.csproj

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <MSBuildCommunityTasksPath Condition=" '$(MSBuildCommunityTasksPath)' == '' ">$(SolutionDir)\packages\MSBuildTasks.1.4.0.88\tools</MSBuildCommunityTasksPath>
    <SetAssemblyVersionEnabled Condition=" Exists('$(MSBuildCommunityTasksPath)\MSBuild.Community.Tasks.targets') ">true</SetAssemblyVersionEnabled>
    <SetAssemblyVersionEnabled Condition=" '$(SetAssemblyVersionEnabled)' == '' ">false</SetAssemblyVersionEnabled>
    <SetAssemblyVersionEnabled Condition=" $(DefineConstants.Contains('OFFICIAL'))">false</SetAssemblyVersionEnabled>
    <UseMSBuildEngine>False</UseMSBuildEngine>
  </PropertyGroup>
  <Choose>
    <When Condition=" Exists('/Applications') ">
      <PropertyGroup>
        <UnityDllLocation>/Applications/Unity/Unity.app/Contents/Frameworks/Managed/UnityEngine.dll</UnityDllLocation>
      </PropertyGroup>
    </When>
    <Otherwise>
      <PropertyGroup>
        <UnityDllLocation>C:\Program Files\Unity\Editor\Data\Managed\UnityEngine.dll</UnityDllLocation>
      </PropertyGroup>
    </Otherwise>
  </Choose>
  <Import Condition=" '$(SetAssemblyVersionEnabled)' == 'true' " Project="$(MSBuildCommunityTasksPath)\MSBuild.Community.Tasks.targets" />
  <Target Name="SetAssemblyVersion" Condition=" '$(SetAssemblyVersionEnabled)' == 'true' " BeforeTargets="PrepareForBuild">
    <GitVersion LocalPath="$(SolutionDir)">
      <Output TaskParameter="CommitHash" PropertyName="CommitHash" />
    </GitVersion>
    <Exec Command="echo $(CommitHash) &gt; &quot;$(ProjectDir)..\Couchbase.Lite.Shared\Properties\version&quot;" />
  </Target>
  <Import Project="..\Couchbase.Lite.Shared\Couchbase.Lite.Shared.projitems" Label="Shared" Condition="Exists('..\Couchbase.Lite.Shared\Couchbase.Lite.Shared.projitems')" />
  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectGuid>{5831782E-A661-4BD0-8D3B-813B963E7B82}</ProjectGuid>
    <OutputType>Library</OutputType>
    <AppDesignerFolder>Properties</AppDesignerFolder>
    <RootNamespace>Couchbase.Lite.Unity</RootNamespace>
    <AssemblyName>Couchbase.Lite</AssemblyName>
    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
    <FileAlignment>512</FileAlignment>
    <ReleaseVersion>1.1</ReleaseVersion>
    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\</SolutionDir>
    <RestorePackages>true</RestorePackages>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    <DebugSymbols>True</DebugSymbols>
    <DebugType>full</DebugType>
    <Optimize>False</Optimize>
    <OutputPath>bin\Debug\</OutputPath>
    <DefineConstants>DEBUG;TRACE;__UNITY__;NET_3_5;</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    <Optimize>True</Optimize>
    <OutputPath>bin\Release\</OutputPath>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
    <DebugType>pdbonly</DebugType>
    <DebugSymbols>true</DebugSymbols>
    <DefineConstants>__UNITY__;NET_3_5;</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
    <Reference Include="System" />
    <Reference Include="UnityEngine">
      <HintPath>vendor\Unity\UnityEngine.dll</HintPath>
    </Reference>
    <Reference Include="ugly_net35">
      <HintPath>..\Couchbase.Lite.Net35\vendor\SQLitePCL\ugly_net35.dll</HintPath>
    </Reference>
    <Reference Include="SQLitePCL.raw">
      <HintPath>..\Couchbase.Lite.Net35\vendor\SQLitePCL\SQLitePCL.raw.dll</HintPath>
    </Reference>
    <Reference Include="Newtonsoft.Json">
      <HintPath>..\Couchbase.Lite.Net35\vendor\JSON.NET\Newtonsoft.Json.dll</HintPath>
    </Reference>
    <Reference Include="System.Data" />
    <Reference Include="ICSharpCode.SharpZipLib">
      <HintPath>..\Couchbase.Lite.Net35\vendor\ICSharpCode\ICSharpCode.SharpZipLib.dll</HintPath>
    </Reference>
  </ItemGroup>
  <ItemGroup>
    <Compile Include="UnityMainThreadScheduler.cs" />
    <Compile Include="UnityLogger.cs" />
    <Compile Include="AOTHelper.cs" />
    <Compile Include="..\Couchbase.Lite.Net35\EnumEx.cs">
      <Link>EnumEx.cs</Link>
    </Compile>
    <Compile Include="..\Couchbase.Lite.Net35\StreamEx.cs">
      <Link>StreamEx.cs</Link>
    </Compile>
    <Compile Include="..\Couchbase.Lite.Net35\StringEx.cs">
      <Link>StringEx.cs</Link>
    </Compile>
  </ItemGroup>
  <ItemGroup>
    <ProjectReference Include="..\Couchbase.Lite.Net35\vendor\Rackspace\Rackspace.Threading\System.Threading.Tasks.Net35\System.Threading.Tasks.Net35.csproj">
      <Project>{DCB5D745-525C-46A1-BFC0-E12F87AB6165}</Project>
      <Name>System.Threading.Tasks.Net35</Name>
    </ProjectReference>
    <ProjectReference Include="..\Couchbase.Lite.Net35\vendor\Rackspace\System.Net.Http\System.Net.Http-net_4_5.csproj">
      <Project>{9862694D-E4FA-418B-8692-A0280FEDDF36}</Project>
      <Name>System.Net.Http-net_4_5</Name>
    </ProjectReference>
    <ProjectReference Include="..\Couchbase.Lite.Net35\vendor\Rackspace\Rackspace.Threading\Rackspace.Threading\Rackspace.Threading.net35-client.csproj">
      <Project>{52CA4A3B-F296-4489-B5F0-AD375D039B35}</Project>
      <Name>Rackspace.Threading.net35-client</Name>
    </ProjectReference>
  </ItemGroup>
  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
  <Target Name="CopyUnityDll" BeforeTargets="PrepareForBuild">
    <Message Text="Copying UnityEngine.dll to project" />
    <Error Condition=" !Exists('$(ProjectDir)vendor\Unity\UnityEngine.dll') AND !Exists('$(UnityDllLocation)') " Text="UnityEngine.dll not found in the default location ($(UnityDllLocation)).  Please copy it to src/Couchbase.Lite.Unity/vendor/Unity" />
    <Copy Condition=" !Exists('$(ProjectDir)vendor\Unity\UnityEngine.dll') " SourceFiles="$(UnityDllLocation)" DestinationFolder="$(ProjectDir)vendor\Unity" />
  </Target>
  <Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$(SolutionDir)\.nuget\NuGet.targets')" />
  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
    <PropertyGroup>
      <ErrorText>This project references NuGet package(s) that are missing on this computer. Enable NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
    </PropertyGroup>
    <Error Condition="!Exists('$(SolutionDir)\.nuget\NuGet.targets')" Text="$([System.String]::Format('$(ErrorText)', '$(SolutionDir)\.nuget\NuGet.targets'))" />
  </Target>
</Project>

Replace the Choose block with simpler:

<PropertyGroup>
 <UnityDllLocation Condition=" '$(OS)' != 'Windows_NT' ">/Applications/Unity/Unity.app/Contents/Frameworks/Managed/UnityEngine.dll </UnityDllLocation>
 <UnityDllLocation Condition=" '$(OS)' == 'Windows_NT' ">C:\Program Files\Unity\Editor\Data\Managed\UnityEngine.dll </UnityDllLocation>
</PropertyGroup>
<Copy Condition="!Exists('$(UnityDllLocation)') " ... />

Note the padding spaces in the Condition attributes. This is required to work around xbuild wonkiness.