add sysroot lower bound to run_constrained

[minrk]

prevents downstream packages from building with older sysroot (#143)

draft because:

• it's unclear if this is an openmpi-specific issue or should be done in sysroot's run_exports
• may need repodata patches for prior 2.17 builds for solver consistency if this is the right thing to do
• it seems like we need guidance from conda-forge core on how best to signal that "when build with sysroot X, linking against this package must also build with sysroot >=X", and when that's likely to be the case

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[h-vetinari]

it's unclear if this is an openmpi-specific issue or should be done in sysroot's run_exports

Given the discussion in conda-forge/linux-sysroot-feedstock#63, I'd suggest you add this to openmpi for now; if at any point it becomes added as a sysroot constraint itself, you can always remove it later.

[minrk]

Thanks! That's useful. If I've read that discussion correctly, it won't have the desired effect when openmpi is just in host, right? That limits the usefulness a bit, I suppose, since that's all linux-64 builds, which are the main ones affected by the current issue.

[minrk]

I think adding -Wl,--allow-shlib-undefined to the wrapper ldflags as done in #159 is the fix for our situation (the tests do exercise building with 2.12), so we don't appear to actually have this transitive requirement. I think it remains unclear if/whether/how this transitive requirement may actually come up and how it should be expressed (seems impossible for host dependencies), but at least openmpi doesn't seem to have it.

I think it's worth adding -Wl,--allow-shlib-undefined as the solution to undefined reference to symbol@GLIBC_2.17, and mentioning that it's in $LDFLAGS to the conda-forge knowledge base somewhere.

[minrk]

I changed my mind, on re-reading various situations from #143, adding this constraint will make it more likely for compilation to succeed in user environments, since building with compiler wrappers is something that's normal to occur for users at runtime, not just building packages in conda-build.

[dalcinl]

@minrk What's the status of this PR? Are you waiting for anything to happen upstream in conda-forge? Or it is just an abandoned idea?

[minrk]

I don't think this really makes sense, so I don't think we should do special things for openmpi here.