Cannot create jar file to upload on AWS Device Farm

I am using Appium test automation framework and i want to upload it on AWS Device Farm. I have updated the pom.xml and zip.xml file. When i run the command 'mvn clean package –-DskipTests=true' i get the following error.

    [INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building 1 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.109 s
[INFO] Finished at: 2016-07-25T14:54:43+05:30
[INFO] Final Memory: 7M/77M
[INFO] ------------------------------------------------------------------------
[ERROR] Unknown lifecycle phase "?-DskipTests=true". You must specify a valid li
fecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id
>:<plugin-artifact-id>[:<plugin-version>]:<goal>. Available lifecycle phases are
: validate, initialize, generate-sources, process-sources, generate-resources, p
rocess-resources, compile, process-classes, generate-test-sources, process-test-
sources, generate-test-resources, process-test-resources, test-compile, process-
test-classes, test, prepare-package, package, pre-integration-test, integration-
test, post-integration-test, verify, install, deploy, pre-clean, clean, post-cle
an, pre-site, site, post-site, site-deploy. -> [Help 1]

Can any one please give me a solution on this?? Previously i was getting mvn is not recognized as an internal or external command, so I installed maven separately.. Please help