in bin/xtimecomposer add the following lines :

sub isCentos7 {
    if (-e "/etc/redhat-release") {
        my $version = `cat /etc/redhat-release`;
        if ($version =~ /CentOS Linux release 7/) {
            return 1;
        }
    }
    return 0;
}

And

elsif (isCentos7()) {
   # Uses the default browser
   $vmargs .= "-vmargs";
   $vmargs .= " -Dcom.xmos.cdt.disableMozillaBrowserCreation=True";
   $vmargs .= " -Dorg.eclipse.swt.browser.UseWebKitGTK=True";
}