Running on CI can trigger bash: line 39: GITHUB_PATH: unbound variable error

[mjpieters]

When running on a CI environment other than Github, using the install-from-binstall-release.sh script but forgetting to include the $CARGO_HOME/bin path in the PATH env var, leads to this error:

bash: line 39: GITHUB_PATH: unbound variable

That's because the set -u bash option is enabled in the script, and GITHUB_PATH is not a variable you can expect to exist on other CI environments.

This can be trivially fixed by using ${GITHUB_PATH:-} instead, which will substitute the empty string if the variable is null. test -n then still exits with 1, achieving the same test result.

[NobodyXu]

Thanks!

I would fix it soon, but I also welcome contributions from community, so if you have a PR I would merge it.