BCP 47 language configFlags lost duirng build

[Kirlif]

Decoding works fine
An example with this short table.xml:

<table version="0.0.2">
   <packages index="1" count="1">
        <package index="0" id="127" name="what.the">
            <specs index="2" count="1">
               <spec index="1" id="17" entryCount="301" name="string">
                 <types index="1" count="3">
                    <type index="0" id="17" configFlags="-es" configFlagsSize="64" entryCount="301"/>
                    <type index="1" id="17" *configFlags="-b+es+419"* configFlagsSize="64" entryCount="301"/>
                    <type index="2" id="17" configFlags="-es-rUS" configFlagsSize="64" entryCount="301"/>
                 </types>
               </spec>
            </specs>
        </package>
   </packages>
</table>

Encoding has trouble
Once built back to .arsc format then again converted to xml:

<table version="0.0.2">
   <packages index="1" count="1">
        <package index="0" id="127" name="what.the">
            <specs index="2" count="1">
               <spec index="1" id="17" entryCount="301" name="string">
                 <types index="1" count="3">
                    <type index="0" id="17" configFlags="-es" configFlagsSize="64" entryCount="301"/>
                    <type index="1" id="17" configFlags="" configFlagsSize="64" entryCount="301"/>
                    <type index="2" id="17" configFlags="-es-rUS" configFlagsSize="64" entryCount="301"/>
                 </types>
               </spec>
            </specs>
        </package>
   </packages>
</table>