Fix net sdk references discovery (dotnet#10569)

* Fix net sdk references discovery

* Do numbers properly

* version filter

src/fsharp/CompilerConfig.fs

@@ -877,8 +877,6 @@ type TcConfig private (data: TcConfigBuilder, validate: bool) =
 #endif
                 None, data.legacyReferenceResolver.HighestInstalledNetFrameworkVersion()
 
-    let systemAssemblies = systemAssemblies
-
     member x.primaryAssembly = data.primaryAssembly
     member x.noFeedback = data.noFeedback
     member x.stackReserveSize = data.stackReserveSize   

src/fsharp/DotNetFrameworkDependencies.fs

@@ -29,7 +29,7 @@ module internal FSharp.Compiler.DotNetFrameworkDependencies
             location
 
     let inline ifEmptyUse alternative filename = if String.IsNullOrWhiteSpace filename then alternative else filename
-    
+
     let getFSharpCoreLibraryName = "FSharp.Core"
     let getFsiLibraryName = "FSharp.Compiler.Interactive.Settings"
     let getDefaultFSharpCoreLocation = Path.Combine(fSharpCompilerLocation, getFSharpCoreLibraryName + ".dll")
@@ -62,15 +62,27 @@ module internal FSharp.Compiler.DotNetFrameworkDependencies
     //          packs\Microsoft.NETCore.App.Ref\sdk-version\netcoreappn.n
     //     we will rely on the sdk-version match on the two paths to ensure that we get the product that ships with the
     //     version of the runtime we are executing on
-    //     Use the reference assemblies for the highest netcoreapp tfm that we find in that location.
+    //     Use the reference assemblies for the highest netcoreapp tfm that we find in that location that is 
+    //     lower than or equal to the implementation version.
+    let zeroVersion = Version("0.0.0.0")
     let version, frameworkRefsPackDirectoryRoot =
         try
-            let version = DirectoryInfo(implementationAssemblyDir).Name
+            let computeVersion version =
+                match Version.TryParse(version) with
+                | true, v -> v
+                | false, _ -> zeroVersion
+
+            let version = computeVersion (DirectoryInfo(implementationAssemblyDir).Name)
             let microsoftNETCoreAppRef = Path.Combine(implementationAssemblyDir, "../../../packs/Microsoft.NETCore.App.Ref")
             if Directory.Exists(microsoftNETCoreAppRef) then
-                Some version, Some microsoftNETCoreAppRef
+                let directory = DirectoryInfo(microsoftNETCoreAppRef).GetDirectories()
+                                |> Array.map (fun di -> computeVersion di.Name)
+                                |> Array.sort
+                                |> Array.filter(fun v -> v <= version)
+                                |> Array.last
+                Some (directory.ToString()), Some microsoftNETCoreAppRef
             else
-               Some version,  None
+               None,  None
         with | _ -> None, None
 
     // Tries to figure out the tfm for the compiler instance.