Remove ISymbianSDK#getPrefixFile. You can get this from ISDKBuildInfo#getPrefixFromVariantCfg().
<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
<name>com.nokia.cdt.debug.cw.symbian</name>
<comment></comment>
<projects>
</projects>
<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
<buildCommand>
<name>org.eclipse.pde.ManifestBuilder</name>
<arguments>
</arguments>
</buildCommand>
<buildCommand>
<name>org.eclipse.pde.SchemaBuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
<natures>
<nature>org.eclipse.pde.PluginNature</nature>
<nature>org.eclipse.jdt.core.javanature</nature>
</natures>
</projectDescription>