mkDerivation: Set meta.position to the source file of the derivation

This requires Nix 1.7.
Partial revert of b09f8110dbcb8bc8a1fcdb3e9a5dddb0956aba96

Didn't mean to commit this change

Signed-off-by: Shea Levy <shea@shealevy.com>
Don't include the code name in the EBS AMI name
Update s3http
npm2nix/patchSrc minor fix

Signed-off-by: Shea Levy <shea@shealevy.com>