The current version of the SonarQube runner plugin for FxCop does not seem to support either this command line parameter or a setting for specifying ad-hoc parameters. If you don't feel like adding this support yourself, one workaround would be to change your fxcopcmd.exe.config
file to add an appropriate AssemblyReferenceResolveMode
setting. e.g.:
<add key="AssemblyReferenceResolveMode" value="StrongNameIgnoringVersion" />