As gcc's "make check", binutils's " make check" will always fail. The toolchain.eclass, in gcc, handles this issue by doing: make check || ewarn "check failed and that sucks :(" in gcc_src_test() function, and the emerge process continues. But the toolchain-binutils.eclass does: make check || die "check failed :(" in toolchain-binutils_src_test() function, and stops the emerge process. From my point of view, the latter is wrong, and "die" should be replaced by "ewarn" as happens in toolchain.eclass
It doesn't break anything, the tests failed if it dies for you. File bugs about broken tests or remove test from your FEATURES.