Gradle native c plugin: Add directory with .h/.lib files to look for while compiling

My gradle build for a native shared library looks like this at the moment:

apply plugin: 'c'
apply plugin: 'visual-studio'

model {
  components {     
    main(NativeLibrarySpec) {
      sources.c {
        source {
          srcDirs "src/main/c"
          include "**/*.c"
        }
        exportedHeaders {
          srcDirs "src/main/headers"
        }
      }
    }
  }
}

How can I add folder that contains .h and .lib files, which I depend on, so that they are found while compiling / linking? The folder I want to add is stored in LIB_NAME env variable.