Github Action: build flock release using cron jobs

[Gang Liao]

We deploy a cron job to automatically trigger CI/CD to build Flock releases every two hours.

For example, logs of previously completed CI tasks can be found in Actions: https://github.com/flock-lab/flock/actions/runs/1702993279

After passing CI/CD, the Actions UI will display a link to download the resulting binary.

After downloading and unzipping, you will see three different packages, including x86 and arm64 architectures.

~/D/result> ls -lah
total 208920
-rw-rw-r--@   1 gangliao  staff    33M Jan 16  2022 flock-aarch64-unknown-linux-gnu-cb3c71b16be0c1b0ce4e41de03f3f41534edb326.tar.gz
-rw-rw-r--@   1 gangliao  staff    34M Jan 16  2022 flock-x86_64-unknown-linux-gnu-cb3c71b16be0c1b0ce4e41de03f3f41534edb326.tar.gz
-rw-rw-r--@   1 gangliao  staff    35M Jan 16  2022 flock-x86_64-unknown-linux-musl-cb3c71b16be0c1b0ce4e41de03f3f41534edb326.tar.gz

$ tar xvf flock-aarch64-unknown-linux-gnu-cb3c71b16be0c1b0ce4e41de03f3f41534edb326.tar.gz
~/D/result> ls -lah target/aarch64-unknown-linux-gnu/release/
total 284360
-rwxr-xr-x@ 1 gangliao  staff    18M Jan 15 20:48 flock
-rwxr-xr-x@ 1 gangliao  staff   121M Jan 15 20:47 flock-cli