System.IO.PathTooLongException on Linux because limit is 255 UTF-8 bytes

[grompe]

Trying to decompile a project with a non-Latin class name too long causes
System.IO.PathTooLongException on Linux filesystem, because in

ILSpy/ICSharpCode.Decompiler/CSharp/ProjectDecompiler/WholeProjectDecompiler.cs

Line 652 in 167192e

static string CleanUpName(string text, bool separateAtDots, bool treatAsFileName, bool treatAsPath)

, the code code is trimming to 255 UTF-16 codepoints and that can result in more than 255 UTF-8 bytes.

I'm not well-versed in the project or C#, but my quick fix was the following:

--- WholeProjectDecompiler.cs
+++ WholeProjectDecompiler.cs
@@ -727,6 +727,17 @@
 			string name = b.ToString();
 			if (extension != null)
 			{
+				if (Environment.OSVersion.Platform == PlatformID.Unix)
+				{
+					int utf8length = Encoding.UTF8.GetByteCount(name);
+					if (utf8length > maxSegmentLength - extension.Length)
+					{
+						byte[] utf8bytes = Encoding.UTF8.GetBytes(name);
+						int i = maxSegmentLength - extension.Length;
+						while (i > 0 && (utf8bytes[i] & 0xC0) == 0x80) i--;
+						name = Encoding.UTF8.GetString(utf8bytes, 0, i);
+					}
+				}
 				// make sure that adding the extension to the filename
 				// does not exceed maxSegmentLength.
 				// trim the name, if necessary.