workaround for jwt 1.5.3 breaking ruby 1.9 support
workaround for jwt 1.5.3 breaking ruby 1.9 support

jwt is included by googleauth.
see https://github.com/jwt/ruby-jwt/issues/132

a-robinson/fluent-plugin-google-cloud,senthilkumar-kj/fluent-plugin-google-cloud,cosmo0920/fluent-plugin-google-cloud,arthurdarcet/fluent-plugin-google-cloud,laramiel/fluent-plugin-google-cloud,GoogleCloudPlatform/fluent-plugin-google-cloud