prep.sh install gcc,rpm-build and download javascript, build.sh

prep.sh:
* default CentOS 5.x installation includes make, so checking failing
** install gcc
** install rpm-build
* download javascript to javascript catalog

new build.sh:
* check if ready to build
* set up CARBON_DISTFILES environment variable (to javascript files)
* create srpm (make srpm)
* patch xapi.spec (ugly, but better than messing up with repo content)
* executing rpm -bb to build binary rpms.

Now compilation process looking like:
wget .../prep.sh ../build.sh
chmod +x *.sh
./prep.sh
./build.sh