CAS symlink target is not canonicalized

Summary

● buildbox-worker.service - Buildbox_worker
     Loaded: loaded (/etc/systemd/system/buildbox-worker.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2020-06-04 19:09:48 UTC; 56min ago
   Main PID: 32549 (buildbox-worker)
      Tasks: 5 (limit: 4514)
     Memory: 51.5M
     CGroup: /system.slice/buildbox-worker.service
             └─32549 /usr/local/bin/buildbox-worker --bots-remote=http://cache.scatterworks.co.uk:50051 --cas-remote=http://127.0.0.1:50011 --request-timeout=60 --bots-retry-delay=60 --platform OSFamily=linux --platform ISA=aarch64 my_bot

Jun 04 19:09:48 ip-172-31-27-213 systemd[1]: Started Buildbox_worker.
Jun 04 19:09:48 ip-172-31-27-213 buildbox-worker[32549]: 2020-06-04T19:09:48.058+0000 [32549:281473678343312] [buildboxworker_config.cpp:49] [INFO] Path to config file is empty, defaulting to status 1
Jun 04 19:09:48 ip-172-31-27-213 buildbox-worker[32549]: 2020-06-04T19:09:48.058+0000 [32549:281473678343312] [buildboxworker_worker.cpp:455] [INFO] Starting build worker with bot ID "my_bot"
Jun 04 20:02:21 ip-172-31-27-213 buildbox-worker[32645]: 2020-06-04T20:02:21.859+0000 [32645:281473849245712] [buildboxcommon_runner.cpp:262] [ERROR] [actionDigest=efa0e33c21ac3f41dfed014b097cea2133682a24c075ef37c187a7b933d7dc25/142] Error executing command: std::invalid_argument exception thrown at [buildboxcommon_client.cpp:324], errMsg = "Cannot create symlink. The target path "../.././../../../../arch/powerpc/include/asm/asm-compat.h" contains substrings not allowed by the API: [/./] or [//]"
Jun 04 20:02:21 ip-172-31-27-213 buildbox-worker[32549]: 2020-06-04T20:02:21.898+0000 [32549:281473644355840] [buildboxworker_actionutils.cpp:176] [INFO] Worker exited with code 1
Jun 04 20:02:21 ip-172-31-27-213 buildbox-worker[32549]: 2020-06-04T20:02:21.899+0000 [32549:281473644355840] [buildboxworker_actionutils.cpp:50] [ERROR] ActionResultFile /tmp/buildboxJLcmAn is an empty file
Jun 04 20:02:21 ip-172-31-27-213 buildbox-worker[32549]: 2020-06-04T20:02:21.899+0000 [32549:281473644355840] [buildboxworker_worker.cpp:196] [ERROR] Caught exception in worker: std::runtime_error exception thrown at [buildboxworker_actionutils.cpp:51], errMsg = "ActionResultFile /tmp/buildboxJLcmAn is an empty file"

[00:00:02] SUCCESS freedesktop-sdk.bst:bootstrap/linux-headers.bst: Staging sources
[--:--:--] START   freedesktop-sdk.bst:bootstrap/linux-headers.bst: Running commands

    make ARCH="arm64" INSTALL_HDR_PATH="/buildstream-install/usr" headers_install
    mkdir -p "/buildstream-install/usr/include/aarch64-linux-gnu/linux"
    mkdir -p "/buildstream-install/usr/include/aarch64-linux-gnu/asm"
    mv "/buildstream-install/usr/include/asm" \
       "/buildstream-install/usr/include/aarch64-linux-gnu/"
    mv "/buildstream-install/usr/include/linux/a.out.h" \
       "/buildstream-install/usr/include/aarch64-linux-gnu/linux/" || true
    mv "/buildstream-install/usr/include/linux/kvm_para.h" \
       "/buildstream-install/usr/include/aarch64-linux-gnu/linux/" || true
    OPTS=()
    if ! "true"; then
      OPTS+=("-n")
    fi
    for p in /cross /usr /usr; do
      OPTS+=("-t" "${p}")
    done
    if [ -x "$(command -v freedesktop-sdk-stripper)" ]; then
      freedesktop-sdk-stripper \
        "${OPTS[@]}" \
        "/buildstream/freedesktop-sdk/bootstrap/linux-headers.bst" \
        "/usr/lib/debug/source/bootstrap/linux-headers.bst" \
        "/usr/lib/debug/dwz/bootstrap/linux-headers.bst" \
        "/usr/lib/debug" \
        "/buildstream-install"
    fi
[--:--:--] START  : Waiting for the remote build to complete
[00:07:52] SUCCESS: Waiting for the remote build to complete
[00:19:34] FAILURE freedesktop-sdk.bst:bootstrap/linux-headers.bst: Running commands
[00:19:37] FAILURE freedesktop-sdk.bst:bootstrap/linux-headers.bst: System error when attempting to execute Action: [std::runtime_error exception thrown at [buildboxworker_actionutils.cpp:51], errMsg = "ActionResultFile /tmp/buildboxJLcmAn is an empty file"]

Not sure if this is a error with bst or buildbox