fix Android compatibility with AGP > 9 hosts in desktop_drop

[loucass]

Follow-up to #495 — @ekuleshov reported that 0.8.2 (Gradle 9.1.0 + Flutter 3.44.8) still fails with the same Could not find method kotlin() error that #495 was meant to fix.

Problem

0.8.2 made the apply plugin: 'kotlin-android' line conditional on AGP major < 9, but left the Kotlin configuration block unconditional:

• android { kotlinOptions { jvmTarget } } — the pre-AGP-9 form, removed in AGP 9

Result: AGP 8 hosts now passed, but AGP 9.1 hosts failed on the kotlin {} DSL itself (kotlin() not found when KGP wasn't applied).

Root cause

Host	Who compiles Kotlin?	kotlin {} unconditional	Conditional (this PR)
AGP < 9	nobody → plugin must apply KGP itself	❌ kotlin() not found*	✅ android.kotlinOptions branch
AGP ≥ 9	AGP built-in Kotlin	✅ works	✅ kotlin.compilerOptions branch

*kotlin extension only exists after KGP is applied.

Fix

Make the configuration block itself conditional:

def agpMajor = com.android.Version.ANDROID_GRADLE_PLUGIN_VERSION.tokenize('.')[0] as int
if (agpMajor < 9) {
    apply plugin: 'kotlin-android'
    android {
        kotlinOptions {
            jvmTarget = JavaVersion.VERSION_1_8.toString()
        }
    }
} else {
    kotlin {
        compilerOptions {
            jvmTarget = org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_1_8
        }
    }
}

Verification

• AGP < 9 host: LocalSend debug APK on Flutter 3.41.9 · AGP 8.12.1 · Gradle 8.13 — run (✓ Built app-debug.apk)
• AGP 9 host: desktop_drop example on AGP 9.1 · Gradle 9.3.1 · Flutter 3.47.1 — run