build log is not available

[jfroche]

We have different packages failing with no build log available. Example:
https://r.ryantm.com/log/azure-cli/2023-04-09.log
https://r.ryantm.com/log/aflplusplus/2023-04-10.log

This could be a problem for #347

I managed to reproduce that locally as well. It looks like we rely on nix log but sometimes the build of a dependency is failing.
For example the azure-cli package:

$ /nix/store/3nqhcyc7vid1npgcd0m7arg5sn325nhz-nix-2.12.0/bin/nix-build --option sandbox true --arg config "{ allowBroken = true; allowUnfree = true; allowAliases = false; }" --arg overlays "[ ]" -A azure-cli
these 2 derivations will be built:
  /nix/store/kb0xqvpcrqgrwdnzvmfcmlnpk03x5hs9-python3.10-azure-cli-core-2.47.0.drv
  /nix/store/5p9wcnay1cd5kj7qjyq2153rzw8a1h9q-python3.10-azure-cli-2.47.0.drv
...
building '/nix/store/kb0xqvpcrqgrwdnzvmfcmlnpk03x5hs9-python3.10-azure-cli-core-2.47.0.drv'...
...
       > ERROR: Could not find a version that satisfies the requirement distro; sys_platform == "linux" (from azure-cli-core) (f
rom versions: none)
       > ERROR: No matching distribution found for distro; sys_platform == "linux"
       >
       For full logs, run 'nix log /nix/store/kb0xqvpcrqgrwdnzvmfcmlnpk03x5hs9-python3.10-azure-cli-core-2.47.0.drv'.
error: 1 dependencies of derivation '/nix/store/5p9wcnay1cd5kj7qjyq2153rzw8a1h9q-python3.10-azure-cli-2.47.0.drv' failed to build

So that

$ /nix/store/3nqhcyc7vid1npgcd0m7arg5sn325nhz-nix-2.12.0/bin/nix log -f . azure-cli
error: build log of 'azure-cli' is not available

So we would need to parse the nix log of all dependencies (or can we filter the dependencies to be built ?) to get the previous error log.

Could we store/catch stdout/stderr when running nix-build instead ?