Travis CI binutils is too old for new binary releases

[Johannes Pfau via D.gnu]

I just tested the new binaries with DMD/travis-CI and of course the
build failed immediately:

https://travis-ci.org/dlang/dmd/jobs/182649710

It looks like this is a binutils bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57017

So I rerun the test with the sysrooted toolchain (this toolchain
includes binutils but doesn't link any system installed libraries
without a -L/usr/lib flag) and this worked fine:

https://travis-ci.org/dlang/dmd/jobs/182653194


So what shall we do about this now? Simply include binutils into the
x86_64 native compiler toolchain? I'm not sure if this has any
drawbacks compared to using the system linker... I could probably build
a 4.9.3 instead of a 4.9.4 compiler as well... None of these solutions
sound nice though.