Added "/sf/" prefix to all bldFile values, as this is what's expected in the package builds.
(Also in comments!)
<?xml version="1.0" encoding="UTF-8"?>
<SystemDefinition name="foundation" schema="2.0.1">
<systemModel>
<layer name="tools" long-name="Tools">
<block name="homescreentools" long-name="Home Screen Tools" tech_domain="ui" level="services" levels="tool install">
<collection name="dtdinstaller" long-name="DTD Installer" level="install">
<component name="dtdinstaller_build" origin-model="foundation">
<unit bldFile="/sf/tools/homescreentools/dtdinstaller/group"/>
</component>
</collection>
<collection name="themeinstaller" long-name="Theme Installer" level="install">
<component name="themeinstaller_build" origin-model="foundation">
<unit bldFile="/sf/tools/homescreentools/themeinstaller/group"/>
</component>
</collection>
<collection name="themetool" long-name="Theme Tool" level="tool">
<component name="themetool_build" origin-model="foundation">
<unit bldFile="/sf/tools/homescreentools/themetool/group"/>
</component>
</collection>
<collection name="homescreentools_info" long-name="Home Screen Tools Info" level="install">
<component unofficial="yes" name="homescreentools_build" long-name="Home Screen Tools Build" origin-model="foundation">
<unit bldFile="/sf/tools/homescreentools/group"/>
</component>
</collection>
</block>
</layer>
</systemModel>
</SystemDefinition>