The atanks spec file should list a BuildRequires on gcc-c++ in order to have a C++ compiler installed to build atanks. More importantly for me (glibc maintainer), the BuildRequires on glibc-headers should be removed since we may or may not keep that subpackage. Having a BuildRequires on gcc-c++ should provide everything you need and meets the new Fedora Packaging Guidelines which require more detailed BuildRequires be present. You can no longer assume a base set of installed buildroot packages. Thank you.
This bug appears to have been reported against 'rawhide' during the Fedora 23 development cycle. Changing version to '23'. (As we did not run this process for some time, it could affect also pre-Fedora 23 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 23 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora23