Add -Xsuppress-deprecated-jvm-target-warning to modules compiled with 1.6

Currently this leads to an unknown argument warning, but it'll be
removed automatically on the next bootstrap.

libraries/scripting/jvm/build.gradle.kts

@@ -1,4 +1,3 @@
-
 plugins {
     kotlin("jvm")
     id("jps-compatible")
@@ -21,7 +20,10 @@ sourceSets {
 }
 
 tasks.withType<org.jetbrains.kotlin.gradle.dsl.KotlinCompile<*>> {
-    kotlinOptions.freeCompilerArgs += "-Xallow-kotlin-package"
+    kotlinOptions.freeCompilerArgs += listOf(
+        "-Xallow-kotlin-package",
+        "-Xsuppress-deprecated-jvm-target-warning"
+    )
 }
 
 tasks.withType<Test> {