-D_GLIBCXX_DEBUG can result in spurious warnings from R CMD check

[wch]

The various builds of R-devel in this Docker image define -D_GLIBCXX_DEBUG, which defines -D_GLIBCXX_ASSERTIONS, which in turn can cause R CMD check to give spurious warnings about abort and printf. This is the same problem as https://stat.ethz.ch/pipermail/r-package-devel/2018q2/002752.html

It might be necessary to remove -D_GLIBCXX_DEBUG for those warnings to go away.

On the other hand, R itself will need to fix the problem -- otherwise this will be a problem for many packages on Fedora 28.