Log or detect errors earlier in library build process

Build errors get logged the https://conan.compiler-explorer.com/failedbuilds.html
But if a different part of the buildprocess, say conan for example, gives errors, the builder will simply stop because of the error (example: https://github.com/compiler-explorer/infra/pull/542), and the error won't end up somewhere useful.

It's also not visible in papertrail, but I wouldn't want to put more useless logging into that either.

Is there any way to log only when an error occurs or alert us? https://github.com/compiler-explorer/infra/blob/main/admin-daily-builds.sh#L98

@mattgodbolt @apmorton

Start with admin-daily-builds.sh around line 98 and compare its handling with the failed-builds page. Review the failure described in infra PR 542 and determine how non-build errors such as Conan failures should be surfaced. Done means actionable error detection or alerting without adding routine noise to Papertrail.

Written by the indexing model from the issue text.