Definition: https://github.com/NixOS/nixpkgs/blob/350fd0044447ae8712392c6b212a18bdf2433e71/pkgs/development/tools/misc/remarkable/remarkable-toolchain/default.nix

which present an "executable" option not propagated to the manifest so the basic hash computation (nix-store --dump) cannot work without `chmod +x` the file.

```
$ cat /var/tmp/sources-unstable-full.json  | jq . | grep -C6  https://storage.googleapis.com/remarkable-codex-toolchain/codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh
    {
      "outputHash": "sha256-ocODUUx2pgmqxMk8J+D+OvqlSHBSay6YzcqnxC9n59w=",
      "outputHashAlgo": "sha256",
      "outputHashMode": "recursive",
      "type": "url",
      "urls": [
        "https://storage.googleapis.com/remarkable-codex-toolchain/codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh"
      ],
      "integrity": "sha256-ocODUUx2pgmqxMk8J+D+OvqlSHBSay6YzcqnxC9n59w=",
      "inferredFetcher": "unclassified"
    },
    {
      "outputHash": "sha256-JKMDRbkvoxwHiTm/o4JdLn3Mm2Ld1LyxTnCCwvnxk4c=",
$ nix-store --dump codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh | sha256sum
0144c6c6b10f88fbf5c154d9e6beb11c771ad71f36d4d0edfc8c3fc01239dda4  -

$ integrity decode "sha256-ocODUUx2pgmqxMk8J+D+OvqlSHBSay6YzcqnxC9n59w="
sha256 a1c383514c76a609aac4c93c27e0fe3afaa54870526b2e98cdcaa7c42f67e7dc

$ ls -lah codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh
-rw-r--r-- 1 tony tony 211M Jan 14  2021 codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh

$ chmod +x codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh
ls -lah codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh
-rwxr-xr-x 1 tony tony 211M Jan 14  2021 codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh

$ integrity decode "sha256-ocODUUx2pgmqxMk8J+D+OvqlSHBSay6YzcqnxC9n59w="
sha256 a1c383514c76a609aac4c93c27e0fe3afaa54870526b2e98cdcaa7c42f67e7dc

$ nix-store --dump codex-x86_64-cortexa9hf-neon-rm10x-toolchain-3.1.2.sh | sha256sum
a1c383514c76a609aac4c93c27e0fe3afaa54870526b2e98cdcaa7c42f67e7dc  -

```