Don't truncate files outside the build chroot.

The list of files passed to Truncate() might contain absolute symlinks
pointing to files outside the chroot, which previously destroyed files on
the build host.

functions/aliases.sh

@@ -36,6 +36,9 @@ Truncate ()
 {
 	for FILE in ${@}
 	do
-		: > ${FILE}
+		if [ ! -L ${FILE} ]
+		then
+			: > ${FILE}
+		fi
 	done
 }