libutil: remove unused FdSource::read

Change-Id: Ie08c9a80dc029ae4e5eb91b09db81166c8a627a3

lix/libutil/serialise.cc

@@ -167,7 +167,6 @@ size_t FdSource::readUnbuffered(char * data, size_t len)
     } while (n == -1 && errno == EINTR);
     if (n == -1) { _good = false; throw SysError("reading from file"); }
     if (n == 0) { _good = false; throw EndOfFile(endOfFileError()); }
-    read += n;
     return n;
 }
 

lix/libutil/serialise.hh

@@ -155,7 +155,6 @@ private:
 struct FdSource : BufferedSource
 {
     int fd;
-    size_t read = 0;
     /** Defaults to "unexpected end-of-file" */
     std::optional<std::string> specialEndOfFileError;
 
@@ -169,7 +168,6 @@ struct FdSource : BufferedSource
     {
         fd = s.fd;
         s.fd = -1;
-        read = s.read;
         return *this;
     }