Deployment targets when using carthage

[Miiha]

Hi,
when using carthage I generate the project using SPM as described in kylef's blog post.
E.g. for iOS when using the built framework in my application, the deployment target of the framework is 13.4, which is too high for me.
When updating the URITemplate.swifts Package.swift to the swift toolchain 5.0 I can make it work using the platforms specifier.

// swift-tools-version:5.0

import PackageDescription

let package = Package(
  name: "URITemplate",
  platforms: [
    .iOS("8.0"),
    .macOS("10.10"),
    .watchOS("2.0"),
    .tvOS("9.0")
  ],
  ...
  ]
)

Is it applicable to update to 5.0?
If not might there be any other way to achieve this when using carthage?