Amazon-eks-ami: Support make ami for 1.13

[monsterxx03]

What would you like to be added:

Support: make 1.13 to build ami for 1.13 worker node

Why is this needed:

We have some customized changes during ami build process(like encrypted ami, pre bake some binaries on host node ...)

Don't known the new s3 location for 1.13 binaries.

[M00nF1sh]

make 1.13 is supported: 😄
https://github.com/awslabs/amazon-eks-ami/blob/master/Makefile#L43
Also, we changed the makefile structure a bit, so you may need to adapt your build process if needed
https://github.com/awslabs/amazon-eks-ami/pull/300

[monsterxx03]

Thanks !