Add Isolated Projects flags for functional tests

https://docs.gradle.org/8.13/userguide/isolated_projects.html#how_do_i_use_it

Author: Goooler

src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt

@@ -425,6 +425,8 @@ abstract class BasePluginTest {
       "--stacktrace",
       // https://docs.gradle.org/current/userguide/configuration_cache.html#config_cache:usage:parallel
       "-Dorg.gradle.configuration-cache.parallel=true",
+      // https://docs.gradle.org/current/userguide/isolated_projects.html#how_do_i_use_it
+      "-Dorg.gradle.unsafe.isolated-projects=true",
     )
 
     fun String.toProperties(): Properties = Properties().apply { load(byteInputStream()) }