LibCore: Return EBADF on unsupported stream operations

Author: https://github.com/timschumi
Commit: 1ca62de558
Pull-request: https://github.com/SerenityOS/serenity/pull/17058
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/gmta ✅

Userland/Libraries/LibCore/MemoryStream.cpp

@@ -49,7 +49,7 @@ void FixedMemoryStream::close()
 
 ErrorOr<void> FixedMemoryStream::truncate(off_t)
 {
-    return Error::from_errno(ENOTSUP);
+    return Error::from_errno(EBADF);
 }
 
 ErrorOr<Bytes> FixedMemoryStream::read(Bytes bytes)