error building linux-pvgrub2-dom0 for fc23 dom0

Build fails, so I re-run the failing command in the chroot with more logging:

bash-4.3# pwd
/home/user/qubes-src/linux-pvgrub2

bash-4.3# dnf --rpmverbosity debug -v -v -v builddep --setopt=proxy=http://localhost:3128/ -y grub2-xen.spec
cachedir: /var/cache/dnf
Loaded plugins: Query, download, playground, config-manager, debuginfo-install, builddep, protected_packages, noroot, needs-restarting, copr, generate_completion_cache, reposync
DNF version: 1.1.6
repo: using cache for: updates
Qubes OS Builder Repository                                                                                                                                                    99 MB/s | 237 kB     00:00    
not found deltainfo for: Qubes OS Builder Repository
not found updateinfo for: Qubes OS Builder Repository
repo: using cache for: fedora
not found deltainfo for: Fedora 23 - x86_64
not found updateinfo for: Fedora 23 - x86_64
updates: using metadata from Fri Mar 11 12:51:10 2016.
qubes-builder-pkgs: using metadata from Sat Mar 12 12:25:11 2016.
fedora: using metadata from Sat Oct 31 17:34:41 2015.
Last metadata expiration check performed 0:00:00 ago on Sat Mar 12 12:53:21 2016.
Completion plugin: Generating completion cache...
Package autoconf-2.69-21.fc23.noarch is already installed, skipping.
Package automake-1.15-4.fc23.noarch is already installed, skipping.
Package binutils-2.25-15.fc23.x86_64 is already installed, skipping.
Package device-mapper-devel-1.02.109-2.fc23.x86_64 is already installed, skipping.
Package freetype-devel-2.6.0-3.fc23.x86_64 is already installed, skipping.
Package gettext-devel-0.19.7-3.fc23.x86_64 is already installed, skipping.
Package git-2.5.0-4.fc23.x86_64 is already installed, skipping.
Package ncurses-devel-5.9-21.20150214.fc23.x86_64 is already installed, skipping.
Package python-2.7.10-8.fc23.x86_64 is already installed, skipping.
Package texinfo-6.0-2.fc23.x86_64 is already installed, skipping.
Package xz-devel-5.2.1-3.fc23.x86_64 is already installed, skipping.
--> Starting dependency resolution
--> Finished dependency resolution
Error: cannot install both glibc-devel-2.22-3.fc23.x86_64 and glibc-devel-2.22-11.fc23.x86_64
(try to add '--allowerasing' to command line to replace conflicting packages)

dnf logging doesnt help. I dislike dnf. rpm says:

bash-4.3# rpm -qa | grep glibc
glibc-common-2.22-11.fc23.x86_64
glibc-2.22-11.fc23.i686
glibc-2.22-11.fc23.x86_64
glibc-headers-2.22-11.fc23.x86_64
glibc-devel-2.22-11.fc23.i686
glibc-devel-2.22-11.fc23.x86_64

So it seems one of the build requirements wants glibc-devel-2.22-3, this must be for the static libc mentioned in the spec file:

%ifarch %{sparc} x86_64
# sparc builds need 64 bit glibc-devel - also for 32 bit userland
BuildRequires:  /usr/lib64/crt1.o glibc-static
%else
# ppc64 builds need the ppc crt1.o
BuildRequires:  /usr/lib/crt1.o glibc-static
%endif

I comment this out of the spec file and rebuild:

/bin/ld: -r and -shared may not be used together

Seems grubs configure go confused about what its building with no static libc in the path.

I restore the spec section, and get the same error again.

I manually install glibc-static in the chroot and it still fails with the same error. 

I suspect there is a bad dependency somewhere, not sure how to find it though.