chore: parameterize the ffi commit hash

[alvin-reyes]

Changes

A simple change to parameterize the ffi commit hash. This is to allow the builder to specify the FFI_COMMIT_HASH when running make all / build command.

Run the following

make all FFI_COMMIT_HASH=38f10cf

Verification

Ran make all with FFI_COMMIT_HASH=38f10cf

"assets": [
    {
      "url": "https://api.github.com/repos/filecoin-project/filecoin-ffi/releases/assets/61646078",
      "id": 61646078,
      "node_id": "RA_kwDODU4Wls4DrKT-",
      "name": "filecoin-ffi-Darwin-standard.tar.gz",
      "label": "",
      "uploader": {
        "login": "filecoin-helper",
        "id": 37553297,
        "node_id": "MDQ6VXNlcjM3NTUzMjk3",
        "avatar_url": "https://avatars.githubusercontent.com/u/37553297?v=4",
        "gravatar_id": "",
        "url": "https://api.github.com/users/filecoin-helper",
        "html_url": "https://github.com/filecoin-helper",
        "followers_url": "https://api.github.com/users/filecoin-helper/followers",
        "following_url": "https://api.github.com/users/filecoin-helper/following{/other_user}",
        "gists_url": "https://api.github.com/users/filecoin-helper/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/filecoin-helper/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/filecoin-helper/subscriptions",
        "organizations_url": "https://api.github.com/users/filecoin-helper/orgs",
        "repos_url": "https://api.github.com/users/filecoin-helper/repos",
        "events_url": "https://api.github.com/users/filecoin-helper/events{/privacy}",
        "received_events_url": "https://api.github.com/users/filecoin-helper/received_events",
        "type": "User",
        "site_admin": false
      },
      "content_type": "application/octet-stream",
      "state": "uploaded",
      "size": 83444471,
      "download_count": 74,
      "created_at": "2022-04-05T19:54:02Z",
      "updated_at": "2022-04-05T19:54:04Z",
      "browser_download_url": "https://github.com/filecoin-project/filecoin-ffi/releases/download/38f10cf6fa078b98/filecoin-ffi-Darwin-standard.tar.gz"

[10d9e]

@alvin-reyes Looks good.