Tests using _R_CXX_NO_REMAP_= true, which compiles C++ code with
R_NO_REMAP defined.  Otherwise as for the fedora-gcc checks:
see https://www.stats.ox.ac.uk/pub/bdr/Rconfig/r-devel-linux-x86_64-fedora-gcc

It is planned that this will become the default in due course, first
for CRAN incoming checks from 2024-04-14.