[tycho-user] Can't resolve target platform if there is not a fragment fo

[laeubi@xxxxxxxxxxxxxx]

I have an Updatesite (http://rxtx.qbang.org/eclipse) that I have 
included in a target file.
The Updatesite provides (native) fragments for macos 32 bit but not for 
64 bit. If I resolve the target on eclipse I get the desired result:

- on 32 bit platform the plugin is avaiable as well as the native fragment
- on 64bit platform, only the plugin is avaiable and no native fragment

but whith tycho build I get the following error:

[INFO] Adding repository http://rxtx.qbang.org/eclipse
[ERROR] Cannot resolve target definition:
[ERROR]   Problems resolving provisioning plan.:
[ERROR]      Unable to satisfy dependency from gnu.io.rxtx.feature.group 
2.1.7.4_v20071016-7B57e7UAXMAAqGAGf to gnu.io.rxtx.macosx 
[2.1.7.3_v20071015].
[ERROR]

The target iself has the following configuration:
<location includeAllPlatforms="false" includeConfigurePhase="false" 
includeMode="slicer" includeSource="true" type="InstallableUnit">
<unit id="gnu.io.rxtx.sdk.feature.group" 
version="2.1.7.4_v20071016-417C7DP1Bh_eEaQJBrHBHg"/>
<repository location="http://rxtx.qbang.org/eclipse/"/>
</location>

So from a users point of view, the 'Unable to satisfy dependency' should 
never happens because of slicer mode, and as described before Eclipse 
happyly resolves the target, so how can I archive the same with tycho?

The envirouments I use for build are

         <environments>
            <environment>
              <os>linux</os>
              <ws>gtk</ws>
              <arch>x86</arch>
            </environment>
            <environment>
              <os>linux</os>
              <ws>gtk</ws>
              <arch>x86_64</arch>
            </environment>
            <environment>
              <os>win32</os>
              <ws>win32</ws>
              <arch>x86</arch>
            </environment>
            <environment>
              <os>win32</os>
              <ws>win32</ws>
              <arch>x86_64</arch>
            </environment>
            <environment>
              <os>macosx</os>
              <ws>cocoa</ws>
              <arch>x86_64</arch>
            </environment>
          </environments>