unresolvable R_X86_64_NONE relocation against symbol `__sF'

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

And another weird problem:

Using a lang/gcc8 compiler patched to use gas and gld from devel/binutils 
2.26.1 (see other thread), when building pkgtools/pkg_install, I get
	/usr/pkg/bin/gld: /var/work/pkgsrc/pkgtools/pkg_install/work/libfetch/libfetch.a(common.o)(.text+0x1e5): unresolvable R_X86_64_NONE relocation against symbol `__sF'
	/usr/pkg/bin/gld: final link failed: Nonrepresentable section on output
	collect2: error: ld returned 1 exit status
	*** [pkg_add] Error code 1
What the hell does that mean?
What's really strange is that pkgtools/pkg_install is the only package from 
my set that fails to build. I can build monstrosities like devel/cmake, 
devel/boost-libs and lang/gcc8 (using said gcc8), but not pkgtools/pkg_install!

Any help?