Mapcache forgets env var CURL_CA_BUNDLE after first request

[dafvid]

Duplicate post to my comment on the original issue to set env vars from config.

Old but still open issue. I can confirm this works fine. For the first request! Are there something somewhere inside mapcache that clears the environment between requests? It seems like it.

System Windows server 2022 IIS 10 + mapcache fast cgi

Steps to reproduce:

1. Set CURL_CA_BUNDLE
2. Make first request
3. Witness one single tile being fetched from a HTTPS-only WMS
4. Make a second request
5. Recieve a SSL certificate problem: unable to get local issuer certificate
6. Restart/kill the fastcgi server
7. Goto 2

If i set the fast cgi to reload after just one request everything works but obviously VERY slow. So my best guess is that the environment get reset between request and the part that sets environment variables only does so on startup.

Originally posted by @dafvid in https://github.com/MapServer/mapcache/issues/251#issuecomment-2493793446