build/platforms: fix missing flags on remote execution platform

Change-Id: Ie3408448a44a87cb099b5d4ef3d902c45669b6fe
Reviewed-on: https://review.monogon.dev/c/monogon/+/4401
Tested-by: Jenkins CI
Reviewed-by: Jan Schär <jan@monogon.tech>
diff --git a/build/platforms/BUILD.bazel b/build/platforms/BUILD.bazel
index c5c9838..bca656a 100644
--- a/build/platforms/BUILD.bazel
+++ b/build/platforms/BUILD.bazel
@@ -55,4 +55,8 @@
         "container-image": "docker://gcr.io/monogon-infra/sandbox",
         "OSFamily": "linux",
     },
+    flags = [
+        "--@toolchain_cc_mngn//buildmode:static",
+        "--@io_bazel_rules_go//go/config:static",
+    ],
 )