ci: mark arm64 minimina step as soft_fail

The arm64 storagebox cache-write infra isn't exercised by any other CI
job currently, and its permission problem (mkdir -p /var/storagebox/...
failing with Permission denied during the cache-write step) is
orthogonal to the minimina build itself. The cargo compile stage on
arm64 succeeds.

Keep the arm64 step running to surface the cargo build and noble arm64
toolchain signal, but mark it soft_fail so PRs aren't blocked on the
storagebox mkdir issue until infra is fixed separately.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: dkijania

buildkite/src/Jobs/Release/Minimina.dhall

@@ -16,6 +16,10 @@ let RunInToolchain = ../../Command/RunInToolchain.dhall
 
 let Arch = ../../Constants/Arch.dhall
 
+let B = ../../External/Buildkite.dhall
+
+let B/SoftFail = B.definitions/commandStep/properties/soft_fail/Type
+
 in  Pipeline.build
       Pipeline.Config::{
       , spec = JobSpec::{
@@ -56,6 +60,7 @@ in  Pipeline.build
             , key = "build-minimina-arm64"
             , target = Size.Arm64
             , docker = None Docker.Type
+            , soft_fail = Some (B/SoftFail.Boolean True)
             }
         ]
       }