Fails with:

make[2]: Entering directory '/builddir/build/BUILD/vfrnav-20230429-build/vfrnav-20230429/doc'
octave-cli -q hamproptbl.m
make[2]: Leaving directory '/builddir/build/BUILD/vfrnav-20230429-build/vfrnav-20230429/doc'
warning: using the gnuplot graphics toolkit is discouraged

The gnuplot graphics toolkit is not actively maintained and has a number
of limitations that are unlikely to be fixed.  Communication with gnuplot
uses a one-directional pipe and limited information is passed back to the
Octave interpreter so most changes made interactively in the plot window
will not be reflected in the graphics properties managed by Octave.  For
example, if the plot window is closed with a mouse click, Octave will not
be notified and will not update its internal list of open figure windows.
The qt toolkit is recommended instead.
error: __go_line__: set: unknown line property 1+;CP 1;, unable to create graphics handle
error: called from
    __plt__>__plt2vv__ at line 502 column 10
    __plt__>__plt2__ at line 248 column 14
    __plt__ at line 135 column 14
    plot at line 240 column 10
    hamproptbl at line 52 column 1
make[2]: *** [Makefile:784: proptbl.cc] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: Entering directory '/builddir/build/BUILD/vfrnav-20230429-build/vfrnav-20230429/doc'
octave-cli -q hartzellf7666a2af.m
                                                                               
                                                                               
       |------------------------Hartzell F7666A-2---------------------------|  
    7 +|+%%%%%%%%+%%%%%%%%%%+%%%%$%%%%+%%%%%%%%%%+%%%%%%%%%%+%%%%%%%%%%+%+-+|  
      +|         +          +    $    +          +   +--------------------+ |  
    6 %|+%%%%%%%%%%%%%%%*AAAAAAAA$AAAAAAAAAAAAAAAAAA%|***?***Approximation|+|  
      %|#########%AAAAAAA###%####$####%##########%A*AAAAAA###Measurements#| |  
      %|#######AAA*#########%####$####%##########%###+$$$?$$$Cowling------+ |  
    5 %|+%%%AAA*%%%%%%%%%%%%%%%%%$%%%%%%%%%%%%%%%%%%%%%%%%%%%AAA*%%%%%%%%+-+|  
      %|#AAA*####%##########%####$####%##########%##########%###AAA####%##  |  
    4 %|A*%%%%%%%%%%%%%%%%%%%%%%%$%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*A*%%%%+-+|  
      %|#########%##########%####$####%##########%##########%#######AAA%##  |  
      %|#########%##########%####$####%##########%##########%#########*AA#  |  
    3 %|+%%%%%%%%%%%%%%%%%%%%%%%%$%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%AA-+|  
      %|#########%##########%####$####%##########%##########%##########%#*A*|  
    2 %|+%%%%%%%%%%%%%%%%%%%%%%%%$%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%+-A|  
      %|#########%##########%####$####%##########%##########%##########%##  |  
      %|#########AF=104.4 (without cowling)######%##########%##########%##  |  
    1 %|+%%%%%%%%%%%%%%%%%%%%%%%%$%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%+-+|  
      +|--------------------------------------------------------------------|  
    0 +-+%%%%%%%%+%%%%%%%%%%+%%%%$%%%%+%%%%%%%%%%+%%%%%%%%%%+%%%%%%%%%%+%+-+   
      5         10         15        20         25         30         35       
                                  Radius [inch]                                
                                                                               
make[2]: Leaving directory '/builddir/build/BUILD/vfrnav-20230429-build/vfrnav-20230429/doc'
warning: using the gnuplot graphics toolkit is discouraged

The gnuplot graphics toolkit is not actively maintained and has a number
of limitations that are unlikely to be fixed.  Communication with gnuplot
uses a one-directional pipe and limited information is passed back to the
Octave interpreter so most changes made interactively in the plot window
will not be reflected in the graphics properties managed by Octave.  For
example, if the plot window is closed with a mouse click, Octave will not
be notified and will not update its internal list of open figure windows.
The qt toolkit is recommended instead.
make[1]: *** [Makefile:686: all-recursive] Error 1
make: *** [Makefile:579: all] Error 2

Reported upstream here: https://gitlab.com/tsailer/vfrnav/-/issues/3

Reproducible: Always