Error when setting makeFile

Error:

Exception thrown while executing model rule: ExternalBuildPlugin.Rules#configureExternalBuildTask(Task, ExternalBuildPlugin.ExternalBuildSpec)
> No signature of method: static com.cisco.gradle.externalbuild.tasks.GnuMake.setMakefile() is applicable for argument types: (java.io.File) values: [path/to/file/file.mak]
  Possible solutions: setMakefile(java.io.File), getMakefile(), makefile(java.lang.Object)

Sample Build Script

apply plugin: 'com.cisco.external-build'
import com.cisco.gradle.externalbuild.ExternalNativeLibrarySpec
import com.cisco.gradle.externalbuild.tasks.GnuMake

model {
    components {
        foo(ExternalNativeLibrarySpec) {
            buildConfig(GnuMake) {
                makeFile 'path/to/file/file.mak'
                targets 'all', 'build', 'debug', 'clean', 'prep'
            }
        }
    }
}

Description

Unable to use plugin successfully, all attempts result in the same error. Attempted to use various methods of setting the make file. I'm unsure if it is operator error, lacking documentation, or a bug. Using version 1.14 of plugin and gradle version 4.10.2.

Happy to help troubleshoot and provide more information. I'm hopeful for the plugin to save me (one inexperienced with custom gradle plugins) writing a version doing the same thing.