Download source code from mozilla using followinn command
mkdir xulrunner19
cd xulrunner19
cvs -d :pserver:anonymous@cvs-mirror.mozilla.org:/cvsroot co -r FIREFOX_3_0_RELEASE mozilla/client.mk
cd mozilla
make -f client.mk checkout MOZ_CO_PROJECT=xulrunner
Create a configuration file xulrunner.mozconfig
Information about mozilla connfig file on Mozila
An example of configuration file is here