Kotlin: compiler_arguments test: Fix running gradle on Windows

Author: igfoo

java/ql/integration-tests/all-platforms/kotlin/compiler_arguments/test.py

@@ -2,4 +2,4 @@
 
 run_codeql_database_create(
     ["gradle build --no-daemon --no-build-cache"], lang="java")
-runSuccessfully(["gradle", "clean"])
+runSuccessfully([get_cmd("gradle"), "clean"])