Fixed build error when F# is not installed.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/branches/3.0@3653 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/AddIns/BackendBindings/FSharp/FSharpBinding/Project/FSharpBinding.fsproj

@@ -107,12 +107,14 @@
       <Private>True</Private>
     </ProjectReference>
   </ItemGroup>
-  <Import Project="$(MSBuildExtensionsPath)\FSharp\1.0\Microsoft.FSharp.Targets" />
-  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
-	     Other similar extension points exist, see Microsoft.Common.targets.
-	<Target Name="BeforeBuild">
+  <Import Project="$(MSBuildExtensionsPath)\FSharp\1.0\Microsoft.FSharp.Targets" Condition="Exists('$(MSBuildExtensionsPath)\FSharp\1.0\Microsoft.FSharp.Targets')" />
+	<Target Name="Clean" Condition="!Exists('$(MSBuildExtensionsPath)\FSharp\1.0\Microsoft.FSharp.Targets')">
+		<!-- F# not found? no need to clean anything -->
 	</Target>
-	<Target Name="AfterBuild">
+	<Target Name="Build" Condition="!Exists('$(MSBuildExtensionsPath)\FSharp\1.0\Microsoft.FSharp.Targets')">
+		<Warning Text="Microsoft.FSharp.Targets not found, skipping F# binding"/>
+	</Target>
+	<Target Name="Rebuild" Condition="!Exists('$(MSBuildExtensionsPath)\FSharp\1.0\Microsoft.FSharp.Targets')">
+		<Warning Text="Microsoft.FSharp.Targets not found, skipping F# binding"/>
 	</Target>
-	-->
 </Project>