build: add automatic retry for transient build errors

This could help resolve problems like
https://github.com/exercism/configlet/runs/2912687343 without manual intervention

>```
> 2021-06-25T09:13:10.1012819Z Verifying dependencies for configlet@4.0.0
> 2021-06-25T09:13:10.1247968Z Prompt: No local packages.json found, download it from internet? -> [forced yes]
> 2021-06-25T09:13:10.1249022Z Downloading Official package list
> 2021-06-25T09:13:10.3332943Z Success Package list downloaded.
> 2021-06-25T09:13:10.3474998Z Installing parsetoml@any version
> 2021-06-25T09:13:10.3480429Z Downloading https://github.com/NimParsers/parsetoml.git using git
> 2021-06-25T09:13:31.7531773Z Tip: 6 messages have been suppressed, use --verbose to show them.
> 2021-06-25T09:13:31.7542800Z Error: Execution failed with exit code 128
> 2021-06-25T09:13:31.7546984Z ... Command: git clone --recursive --depth 1 -b v0.6.0 https://github.com/NimParsers/parsetoml.git C:\Users\RUNNER~1\AppData\Local\Temp\nimble_4576\githubcom_NimParsersparsetomlgit
> 2021-06-25T09:13:31.7549662Z ... Output: Cloning into 'C:\Users\RUNNER~1\AppData\Local\Temp\nimble_4576\githubcom_NimParsersparsetomlgit'...
> 2021-06-25T09:13:31.7552513Z ... fatal: unable to access 'https://github.com/NimParsers/parsetoml.git/': Failed to connect to github.com port 443: Timed out
> 2021-06-25T09:13:31.7853877Z Verifying dependencies for configlet@4.0.0
> 2021-06-25T09:13:31.8028489Z Reading official package list
> 2021-06-25T09:13:31.8137370Z Checking for parsetoml@any version
> 2021-06-25T09:13:31.8138125Z Installing parsetoml@any version
> 2021-06-25T09:13:31.8138720Z Reading official package list
> 2021-06-25T09:13:31.8142512Z Downloading https://github.com/NimParsers/parsetoml.git using git
> 2021-06-25T09:13:32.0336639Z Cloning latest tagged version: v0.6.0
> 2021-06-25T09:13:53.1332957Z Error: Execution failed with exit code 128
> 2021-06-25T09:13:53.1335194Z ... Command: git clone --recursive --depth 1 -b v0.6.0 https://github.com/NimParsers/parsetoml.git C:\Users\RUNNER~1\AppData\Local\Temp\nimble_6936\githubcom_NimParsersparsetomlgit
> 2021-06-25T09:13:53.1336780Z ... Output: Cloning into 'C:\Users\RUNNER~1\AppData\Local\Temp\nimble_6936\githubcom_NimParsersparsetomlgit'...
> 2021-06-25T09:13:53.1337998Z ... fatal: unable to access 'https://github.com/NimParsers/parsetoml.git/': Failed to connect to github.com port 443: Timed out
> 2021-06-25T09:13:53.1446019Z ##[error]Process completed with exit code 1.
>```