Use frame-pointer unwinding for Shardok profiles (#8786)

ci/BUILD.bazel

@@ -230,6 +230,14 @@ oci_image(
     name = "shardok_server_image_arm64",
     base = "@ubuntu_24_04_linux_arm64_v8",
     entrypoint = ["/app/shardok-server"],
+    env = {
+        # The default libgcc unwinder does not use the interrupted thread's ARM64 signal context,
+        # producing correct leaf samples with unrelated parent frames. The production binary is
+        # built with frame pointers, so select gperftools' context-aware frame-pointer unwinder
+        # before its static initializer chooses an implementation.
+        "TCMALLOC_STACKTRACE_METHOD": "generic_fp",
+        "TCMALLOC_STACKTRACE_METHOD_VERBOSE": "1",
+    },
     exposed_ports = [
         "40042/tcp",
         "40052/tcp",