using mkoctfile with autotools

[c.]

Hi,

I am building a standalone program that links to Octave and I'm trying to use 
mkoctfile in an autoconf test to determine appropriate include and link flags, 
for example:

AC_SUBST(OCTAVE_CPP_FLAGS, "$(mkoctfile -p CPPFLAGS)")

the problem is that if a value is given for CPPFLAGS, in an environment variable
or on the configure command line, e.g.

./configure CPPFLAGS=-I/my_includes_dir

then "mkoctfile -p CPPFLAGS" will return "/my_includes_dir" rather than the the 
preprocessor flags needed to include Octave, and similar problems occur with 
other
variable like CXXFLAGS or CXXPICFLAG and so on …

Is this behaviour of mkoctfile intended? Is there any way I can work around it? 

Thanks,
c.