exclude unused dependencies

[confile]

I want to exclude dependencies which are included by other libs and not used. For example using:

gwt {
    version="2.6.0"
    gin.version = '2.1.2' // must not be defined if it is under dependencies

    dependencies=[
            'org.slf4j:slf4j-api:1.7.5'
        ]
}

I get an error if another version of slf4j-api is used. How can I exclude older versions?

[oniseijin]

I did this in the BuildConfig (outside of the gwt)
runtime ('com.sencha.gxt:gxt-themebuilder:3.1.1'){
excludes 'xercesImpl'
excludes 'slf4j-jdk14'
}
Although, I don't think you need to add that dependency in the gwt section for it to work.