Report write() errno instead of just plain -1

Co-Authored-By: Michael Chirico <[email protected]>

Author: aitap

src/fwrite.c

@@ -845,7 +845,7 @@ void fwriteMain(fwriteMainArgs args)
         free(buffPool);
         free(zbuffPool);
         deflateEnd(&strm);
-        STOP(_("Failed to write gzip header. Write returned %d"), ret0);
+        STOP(_("Failed to write gzip header. Write returned %d"), errwrite);
         // # nocov end
       }
     }