Due to the scourge of symlinked git repositories, building the
configuration files in dictionaries fails on cygwin because the native
xsltproc cannot understand cygwin symlinks; work around that with a
new gb_Helper_symlinked_native function.
Should be reverted once git sub modules liberate us from the scourge.

Change-Id: Idc48da9b60348dc66160219909479c3c83daeaf2