Staged-recipes: C/C++ library review

[isuruf]

cc @conda-forge/staged-recipes

Now that we are using conda-build=3, there is useful information to check whether a C/C++ library should be in run explicitly or implicitly.

If you see,

WARNING (tesseract,bin/tesseract): Needed DSO lib/liblzma.so.5 found in ['xz']
WARNING (tesseract,bin/tesseract): .. but ['xz'] not in reqs/run, i.e. it is overlinked (likely) or a missing dependency (less likely)

at the end of the build log, that means xz is directly linked and should be pinned. Therefore xz must be added to host and run and will be pinned using pin_run_as_build.

EDIT: There might be the case that it is overlinked, but what I find is that it is not usually the case

[scopatz]

The build should fail if it is truly a problem. Is there a way to turn these warnings into errors that have a non-zero exit code?

[isuruf]

Issue is that until we move to the anaconda 5 compilers, there are false positives like libstdc++, libc++, etc. I think there is a flag to turn them into errors.

[scopatz]

Hmm It sounds like we don't have the right tooling for this then, right now. Maybe we could make a wrapper process than then filters out the libstdc++, libc++, etc. but raises an error otherwise

[mariusvniekerk]

Could we extract some of those messages and send them as comments in the PR? It could get a tad noisy (not sure if there is order stability in there)