lsst-wcslib fail on CentOS 5.11. This failure is similar to DM-7774 and is fixed through the same method.
See yet another VERY long log:
Reproduce conda-lsst problems using lsstsw
Investigate CentOS5 with GCC 5.2.0
Investigate CentOS5 with alternative GCC versions
Investigate using Conda Forge's docker image
Conda binary distribution improvements
conda-lsst Linux lsst-fftw build failure.
This seems to be an environment problem but I don't know what's causing it or why using -std=gnu89 fixes it.
See the commit in my v12.1 release branch. Which will be merged when the v12.1 release is complete.
This fix is known but no longer necessary. This is a problem with the Conda packaged GCC (4.8.5). But is not a problem in ContinuumIO's system GCC (5.2.0).