Never mind. I was able to add it to the build file like so:

def buildForARM = project.findProperty("kotlin.native.cocoapods.target") == "ios_arm"
    if (buildForARM) {
        iosArm32("ios32")
        iosArm64("ios64")

        def iosMain = sourceSets.maybeCreate("iosMain")
        sourceSets["ios64Main"].dependsOn(iosMain)
        sourceSets["ios32Main"].dependsOn(iosMain)

    } else {
        iosX64("ios")
        macosX64("macosX64")

        def iosMain = sourceSets.maybeCreate("iosMain")
        sourceSets["macosX64Main"].dependsOn(iosMain)
    }

but it fails in the build do to trying to build the iOS source as macOS/AppKit source:

Showing All Messages
e: library/PlatformIos.kt: (10, 17): Unresolved reference: UIKit

So I guess some tweaking under the covers is needed here.