Remove Platform.HasUNCSupport query

src/System.Management.Automation/CoreCLR/CorePsPlatform.cs

@@ -217,13 +217,6 @@ namespace System.Management.Automation
 
         }
 
-        // Linux has no support for UNC, just mounts in a single rooted hierarchy
-        // the UNC equivalent of a "network drive" aka mount would be the mount itself
-        internal static bool HasUNCSupport()
-        {
-            return IsWindows;
-        }
-
         // Linux uses .net to query file attributes
         internal static bool UseDotNetToQueryFileAttributes()
         {

src/System.Management.Automation/engine/Utils.cs

@@ -1129,12 +1129,12 @@ namespace System.Management.Automation
 
         internal static bool PathIsUnc(string path)
         {
-            if (!Platform.HasUNCSupport())
-            {
-                return false;
-            }
+#if LINUX
+            return false;
+#else
             Uri uri;
             return !string.IsNullOrEmpty(path) && Uri.TryCreate(path, UriKind.Absolute, out uri) && uri.IsUnc;
+#endif
         }
 
         internal class NativeMethods

src/System.Management.Automation/namespaces/FileSystemProvider.cs

@@ -685,15 +685,11 @@ namespace Microsoft.PowerShell.Commands
         /// <returns></returns>
         internal static string GetUNCForNetworkDrive(string driveName)
         {
-            // Porting note: on systems that do not support UNC paths, the UNC equivalent is the path itself
-            if (Platform.HasUNCSupport())
-            {
-                return WinGetUNCForNetworkDrive(driveName);
-            }
-            else
-            {
-                return driveName;
-            }
+#if LINUX
+            return driveName;
+#else
+            return WinGetUNCForNetworkDrive(driveName);
+#endif
         }
 
         private static string WinGetUNCForNetworkDrive(string driveName)