Why rasqal configuration can't recognize the already raptor library on cygwin?

I am trying to install rasqal 0.9.20 library http://librdf.org/rasqal/ onto a windows 7 machine with cygwin.Earlier i have successfully installed the raptor-2.2.0 library http://librdf.org/raptor/ and i can verify this with the rapper tool was created after the installation(./configure , ./make ,/make install)

The error that i am getting from the configuration of rasqal is :

    ./configure --enable-raptor2  
...  
    checking for raptor... configure: error: Raptor2 is not installed - see http://librdf.org/raptor/ to get a version newer than 1.9.0

I can't find a way to fix it. The code from the cofigure file that handles this flag is the below :

11840 # raptor is REQUIRED despite the checking here
11841 RAPTOR_MIN_VERSION=1.4.19
11842 RAPTOR_MAX_VERSION=1.8.99
11843 RAPTOR2_MI开发者_开发百科N_VERSION=1.9.0
11844
11845 raptor2=no
11846 # Check whether --enable-raptor2 was given.
11847 if test "${enable_raptor2+set}" = set; then :
11848   enableval=$enable_raptor2; raptor2="$enableval"
11849 else
11850   raptor2="no"
11851 fi

Raptor 2.0.0 uses only pkg-config to provide configuration information, raptor-config was removed. The same applies to rasqal itself, the rasqal-config program will go away at some point. The --enable-raptor2 option to rasqal and librdf was for testing the beta raptor2, and it has been removed from rasqal 0.9.22 and librdf GIT head.

Set PKG_CONFIG_PATH to include the correct path:

env PKG_CONFIG_PATH=/usr/local/lib/pkgconfig ./configure

Another method, if available on your system, is to define the environment variable in /etc/environment:

PKG_CONFIG_PATH=/usr/local/lib/pkgconfig