XML-Security-C: configure: error: unable to find xerces header files

I am trying to install Shibboleth 2 SP following this guide:
Building the Native Shibboleth 2 SP from Source on Linux

I configure and built log4shib successfully, and then I tried to build Xerces-C++ 3.1.1 but it gave me a warning: WARNING: unrecognized options: --disable-netaccessor-libcurl and i solved this issue without using that option because is not available in 3.1, "--disable-netaccessor-libcurl" is not listed on:
http://xerces.apache.org/xerces-c/build-3.html

Then I built it whitout get any error o warning.
The third step is to install XML-Security-C but when i run:

./configure --without-xalan --disable-static --prefix=/opt/shibboleth-sp

i get this error:

configure: error: unable to find xerces header files

I treid to export the path:

export PATH=$HOME/opt/shibboleth-sp/bin:$PATH
export LD_LIBRARY_PATH=$HOME/opt/shibboleth-sp/lib:$LD_LIBRARY_PATH
export XERCESCROOT=$HOME/opt/shibboleth-sp:$XERCESCROOT

and as suggested by @Brian:

export CPPFLAGS=$HOME/opt/shibboleth-sp/include
export CFLAGS=$HOME/opt/shibboleth-sp/include

and trying to install again, but doesn't work.

In the folder /opt/shibboleth-sp i have this folders (in /shibboleth-sp i don't have a folder called xercesc but this is inside /include):

/bin/
    DOMCount (file)
    SAX2Count (file)
    SAX2Print (file)
    etc..
/include/
    log4shib
    xercesc
        dom
        framework
        internal
        parsers
        sax
        etc..
/lib/
    liblog4shib.so
    libxerces-c.so
    etc..
/share/
    aclocal

I hope someone can help me.
Thanks for your time.

In your setting, give ./configure the flag --with-xerces=/opt/shibboleth-sp this should find the xerces header files when xerces was installed properly.