--with-cxsparse-includedir option is ignored

[c.]

Hi,

I am trying to build Octave 4.2 on a machine with Scientific Linux release 6.6 
(Carbon).
This machine uses an environmental modules system therefore many libraries, 
including SuiteSparse 
are installed in non-standard locations.

I am configuring with 

  ../configure <...> \
               --with-colamd-includedir=$mkSuitesparseInc \
               --with-colamd-libdir=$mkSuitesparseLib \
               --with-amd-libdir=$mkSuitesparseLib \
               --with-amd-includedir=$mkSuitesparseInc \
               --with-camd-libdir=$mkSuitesparseLib \
               --with-camd-includedir=$mkSuitesparseInc \
               --with-cholmod-libdir=$mkSuitesparseLib \
               --with-cholmod-includedir=$mkSuitesparseInc \
               --with-ccolamd-includedir=$mkSuitesparseInc \
               --with-ccolamd-libdir=$mkSuitesparseLib  \
               --with-cxsparse-libdir=$mkSuitesparseLib \
               --with-cxsparse-includedir=$mkSuitesparseInc \
               --with-umfpack-includedir=$mkSuitesparseInc \
               --with-umfpack-libdir=$mkSuitesparseLib 
              
The configure phase fails with the following message:

  checking for cs_di_sqr in -lcxsparse... yes
  checking whether CXSparse is version 2.2 or later... no
  configure: error: CXSparse library is too old (< version 2.2).  Upgrade 
CXSparse (SuiteSparse) or configure Octave with --disable-cxsparse"

The error message is not very useful because the problem is not with the 
version of CXSparse avaialble (the available version is > 3.0), checking 
config.log I see:

  configure:43472: checking whether CXSparse is version 2.2 or later
  configure:43523: g++ -std=gnu++11 -E  -fPIC  conftest.cpp
  conftest.cpp:96:24: fatal error: cs.h: No such file or directory

So it seems the directory passed to --with-cxsparse-includedir is not being 
added to the compilation flags (while it is added when testing for, e.g., 
cholmod), indeed adding "CPPFLAGS=-I$mkSuitesparseInc" is a workaround for this 
problem.

Is this a configuration bug? Does anyone know if it affects the development 
branch? Should I submit it to the tracker?

c.