possible mkoctfile bug on 4.2.0

[Marco Atzeri]

Trying to build control package with octave-4.2.0 on cygwin I noticed
that the CXX setting seems to not be preserved:

$ mkoctfile -p CXX
g++ -std=gnu++11

while "-std=gnu++11" seems disappear on invocation by Makefile
---------------------------------------------------------------
make: Entering directory 
'/cygdrive/e/cyg_pub/devel/octave-forge/arch/octave-control-3.0.0-2.x86_64/build/control/src'
tar -xzf slicot.tar.gz
/usr/bin/mkoctfile-4.2.0.exe --verbose __control_helper_functions__.cc
g++ -c   -I/usr/include/octave-4.2.0/octave/.. 
-I/usr/include/octave-4.2.0/octave   -fopenmp -ggdb -O2 -pipe 
-fdebug-prefix-map=/pub/devel/octave-forge/arch/octave-control-3.0.0-2.x86_64/build=/usr/src/debug/octave-control-3.0.0-2 
-fdebug-prefix-map=/pub/devel/octave-forge/arch/octave-control-3.0.0-2.x86_64/src/control-3.0.0=/usr/src/debug/octave-control-3.0.0-2 
   __control_helper_functions__.cc -o __control_helper_functions__.o
In file included from 
/usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/cstdint:35:0,
                 from /usr/include/octave-4.2.0/octave/octave-config.h:64,
                 from /usr/include/octave-4.2.0/octave/oct.h:26,
                 from is_real_scalar.cc:28,
                 from __control_helper_functions__.cc:1:
/usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/c++0x_warning.h:32:2: 
error: #error This file requires compiler and library support for the 
ISO C++ 2011 standard. This support must be enabled with the -std=c++11 
or -std=gnu++11 compiler options.
----------------------------------------------------------------------

The Makefile is just

# helper functions
__control_helper_functions__.oct: __control_helper_functions__.cc
        $(MKOCTFILE) __control_helper_functions__.cc

Am I missing something, or it is a bug ?

Regards
Marco