Pkg install struct - octave 5.1 from flatpak, mint 18/ubuntu

[pavel]

Hi,

upon installing octave 5.1 from flatpak I wanted to recompile the 
packages needed for my project for new octave. Previously I was using 
octave 4.2.2, all packages compiled in home/octave. OS Mint 18 = Ubuntu 
16.04. I uninstalled all packages (pkg uninstall) and started installing 
again one by one.

When installing struct I get the following error:

octave:13> pkg install -forge struct
In file included from error-helpers.cc:22:
error-helpers.h:31:22: error: ‘octave_execution_exception’ does not name 
a type; did you mean ‘make_execution_exception’?
 void c_verror (const octave_execution_exception&, const char *, ...);
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
                      make_execution_exception
error-helpers.cc:36:17: error: ‘octave_execution_exception’ does not 
name a type; did you mean ‘make_execution_exception’?
 c_verror (const octave_execution_exception&, const char *fmt, ...)
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~
                 make_execution_exception
error-helpers.cc: In function ‘void _p_error(const char*, ...)’:
error-helpers.cc:60:8: error: ‘cerr’ is not a member of ‘std’
   std::cerr << msg;
        ^~~~
error-helpers.cc:60:8: note: ‘std::cerr’ is defined in header 
‘<iostream>’; did you forget to ‘#include <iostream>’?
error-helpers.cc:23:1:
+#include <iostream>

error-helpers.cc:60:8:
   std::cerr << msg;
        ^~~~
make: *** [Makefile:40: error-helpers.o] Error 1
make: Entering directory „/tmp/oct-BOaV4z/struct-1.0.15/src“
CXXFLAGS="-O2 -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fexceptions 
-fstack-protector-strong -grecord-gcc-switches 
-Wno-deprecated-declarations" /app/bin/mkoctfile-5.1.0 -c error-helpers.cc
make: Leaving directory „/tmp/oct-BOaV4z/struct-1.0.15/src“

pkg: error running `make' for the struct package.
error: called from
    configure_make at line 99 column 9
    install at line 184 column 7
    pkg at line 441 column 9

Thanks a lot for any hints.

Best regards,

Pavel.