Exclude J9 from MALLOC_CHECK_ default test env

J9 hits a pre-existing, unrelated glibc heap-corruption bug that MALLOC_CHECK_ now surfaces as a hard abort; gate it off until that's investigated separately.

Author: jbachorik

build-logic/conventions/src/main/kotlin/com/datadoghq/profiler/ProfilerTestPlugin.kt

@@ -208,11 +208,14 @@ class ProfilerTestPlugin : Plugin<Project> {
             // Turn silent glibc heap corruption (e.g. a use-after-free write into a
             // freed chunk) into an immediate, attributable SIGABRT instead of a crash
             // much later in an unrelated allocation. Only meaningful against glibc's
-            // own malloc: skip on musl (no MALLOC_CHECK_ support) and skip whenever a
-            // sanitizer/allocator already replaces malloc via LD_PRELOAD.
+            // own malloc: skip on musl (no MALLOC_CHECK_ support), skip whenever a
+            // sanitizer/allocator already replaces malloc via LD_PRELOAD, and skip on
+            // J9 (its own allocator usage trips a pre-existing, unrelated heap
+            // corruption that needs separate investigation).
             if (PlatformUtils.currentPlatform == Platform.LINUX &&
                 !PlatformUtils.isMusl() &&
-                !testEnv.containsKey("LD_PRELOAD")
+                !testEnv.containsKey("LD_PRELOAD") &&
+                !PlatformUtils.isTestJvmJ9()
             ) {
                 put("MALLOC_CHECK_", "3")
                 put("MALLOC_PERTURB_", (1..255).random().toString())