Use BitConverter.IsLittleEndian directly

This allows the JIT can optimize away the unused branch

src/ImageSharp/MetaData/Profiles/ICC/DataWriter/IccDataWriter.cs

@@ -11,8 +11,6 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
     /// </summary>
     internal sealed partial class IccDataWriter : IDisposable
     {
-        private static readonly bool IsLittleEndian = BitConverter.IsLittleEndian;
-
         /// <summary>
         /// The underlying stream where the data is written to
         /// </summary>
@@ -179,7 +177,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
         /// <returns>The number of bytes written</returns>
         private unsafe int WriteBytes(byte* data, int length)
         {
-            if (IsLittleEndian)
+            if (BitConverter.IsLittleEndian)
             {
                 for (int i = length - 1; i >= 0; i--)
                 {