toolchain.eclass: depend on sys-devel/binutils:*

GCC doesn't build in Gentoo at least without GNU Binutils. It is possible
but it requires some work. It's not clear to me if some of that work
needs to happen in LLVM upstream too (see below).

In commits 7011340a0f and
a7c2759682, I tried to get things building
with Clang's assembler but didn't get it over the line. I think I remember
Arfrever and I coming up with a few later drafts (?) on IRC in #gentoo-hardened
but I didn't commit any of it as it didn't work in the end anyway.

But see https://briancallahan.net/blog/20240122.html which tackles at least
one of the issues I ended up hitting before.

In any case, add the dependency for now to keep things working.

Closes: https://bugs.gentoo.org/936271
Signed-off-by: Sam James <sam@gentoo.org>

eclass/toolchain.eclass

@@ -353,6 +353,7 @@ fi
 
 BDEPEND="
 	app-alternatives/yacc
+	sys-devel/binutils:*
 	>=sys-devel/flex-2.5.4
 	nls? ( sys-devel/gettext )
 	test? (