Ditch P/Invoke for detecting OSX as it's a detected platform since .NET 3.5.

DepotDownloader/CDRManager.cs

@@ -230,7 +230,7 @@ namespace DepotDownloader
 
             if ( platform == PlatformID.Win32NT )
                 platformStr = "windows";
-            else if ( Util.IsMacOSX() )
+            else if ( platform == PlatformID.MacOSX )
                 platformStr = "macos";
             
             foreach ( var blobField in appInfoBlob.FileSystems )
@@ -266,7 +266,7 @@ namespace DepotDownloader
 
                 if (platform == PlatformID.Win32NT)
                     platformSuffix = "-win32";
-                else if (platform == PlatformID.Unix && !Util.IsMacOSX())
+                else if (platform == PlatformID.Unix)
                     platformSuffix = "-linux";
 
                 foreach (var blobField in serverAppInfoBlob.FileSystems)
@@ -301,7 +301,7 @@ namespace DepotDownloader
                 }
                 else if ( platform == PlatformID.Win32NT )
                     appIDs.Add( 5 );
-                else if ( platform == PlatformID.Unix && !Util.IsMacOSX() )
+                else if ( platform == PlatformID.Unix)
                     appIDs.Add( 4 );
 
                 // Half-Life Base Content

DepotDownloader/Util.cs

@@ -11,49 +11,6 @@ namespace DepotDownloader
 {
     static class Util
     {
-        [DllImport( "libc" )]
-        static extern int uname( IntPtr buf );
-
-        static int _isMacOSX = -1;
-
-        // Environment.OSVersion.Platform returns PlatformID.Unix under Mono on OS X
-        // Code adapted from Mono: mcs/class/Managed.Windows.Forms/System.Windows.Forms/XplatUI.cs
-        public static bool IsMacOSX()
-        {
-            if ( _isMacOSX != -1 )
-                return _isMacOSX == 1;
-
-            IntPtr buf = IntPtr.Zero;
-
-            try
-            {
-                // The size of the utsname struct varies from system to system, but this _seems_ more than enough
-                buf = Marshal.AllocHGlobal( 4096 );
-
-                if ( uname( buf ) == 0 )
-                {
-                    string sys = Marshal.PtrToStringAnsi( buf );
-                    if ( sys == "Darwin" )
-                    {
-                        _isMacOSX = 1;
-                        return true;
-                    }
-                }
-            }
-            catch
-            {
-                // Do nothing?
-            }
-            finally
-            {
-                if ( buf != IntPtr.Zero )
-                    Marshal.FreeHGlobal( buf );
-            }
-
-            _isMacOSX = 0;
-            return false;
-        }
-
         public static string ReadPassword()
         {
             ConsoleKeyInfo keyInfo;