Configuring NIX_SSL_CERT_FILE for self-hosted Linux runners when needed

[vroad]

I set up my self-hosted runner on AWS with philips-labs/terraform-aws-github-runner, and found that python programs fails to fetch from HTTPS URLs without environment variable NIX_SSL_CERT_FILE. Only occured with Amazon Linux 2 AMIs, with Ubuntu AMIs this action just worked fine.

Can we somehow detect this situation and automatically set this environment variable? Currenly, the action only sets the variable on macOS runners.

install-nix-action/install-nix.sh

Lines 72 to 78 in 451e611

	if [[ $OSTYPE =~ darwin ]]; then
	# macOS needs certificates hints
	cert_file=/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt
	echo "NIX_SSL_CERT_FILE=$cert_file" >> "$GITHUB_ENV"
	export NIX_SSL_CERT_FILE=$cert_file
	sudo launchctl setenv NIX_SSL_CERT_FILE "$cert_file"
	fi

[amarshall]

Possibly related: #145