Ensure Android SDK license files always have all license.

Sometime on CI it may happen that file already exists, but does not
contain all required licenses.

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseGradleIT.kt

@@ -53,24 +53,39 @@ abstract class BaseGradleIT {
 
     // https://developer.android.com/studio/intro/update.html#download-with-gradle
     fun acceptAndroidSdkLicenses() = defaultBuildOptions().androidHome?.let {
-        val sdkLicenses = File(it, "licenses")
-        sdkLicenses.mkdirs()
+        val sdkLicensesDir = it.resolve("licenses")
+        if(!sdkLicensesDir.exists()) sdkLicensesDir.mkdirs()
 
-        val sdkLicense = File(sdkLicenses, "android-sdk-license")
-        if (!sdkLicense.exists()) {
-            sdkLicense.createNewFile()
-            sdkLicense.writeText(
-                """
-                8933bad161af4178b1185d1a37fbf41ea5269c55
-                d56f5187479451eabf01fb78af6dfcb131a6481e
-                24333f8a63b6825ea9c5514f83c2829b004d1fee
-                """.trimIndent()
+        val sdkLicenses = listOf(
+            "8933bad161af4178b1185d1a37fbf41ea5269c55",
+            "d56f5187479451eabf01fb78af6dfcb131a6481e",
+            "24333f8a63b6825ea9c5514f83c2829b004d1fee",
+        )
+        val sdkPreviewLicense = "84831b9409646a918e30573bab4c9c91346d8abd"
+
+        val sdkLicenseFile = sdkLicensesDir.resolve("android-sdk-license")
+        if (!sdkLicenseFile.exists()) {
+            sdkLicenseFile.createNewFile()
+            sdkLicenseFile.writeText(
+                sdkLicenses.joinToString(separator = "\n")
             )
+        } else {
+            sdkLicenses
+                .subtract(
+                    sdkLicenseFile.readText().lines()
+                )
+                .forEach {
+                    sdkLicenseFile.appendText("$it\n")
+                }
         }
 
-        val sdkPreviewLicense = File(sdkLicenses, "android-sdk-preview-license")
-        if (!sdkPreviewLicense.exists()) {
-            sdkPreviewLicense.writeText("84831b9409646a918e30573bab4c9c91346d8abd")
+        val sdkPreviewLicenseFile = sdkLicensesDir.resolve("android-sdk-preview-license")
+        if (!sdkPreviewLicenseFile.exists()) {
+            sdkPreviewLicenseFile.writeText(sdkPreviewLicense)
+        } else {
+            if (sdkPreviewLicense != sdkPreviewLicenseFile.readText().trim()) {
+                sdkPreviewLicenseFile.writeText(sdkPreviewLicense)
+            }
         }
     }