Effectively reverts changes that came from
9d58bb6e3e which doesn't seem to be needed
anymore. These got carried into chromium-binary-build-system when it was
introduced. We need libstdc++ from the gcc:lib package, which is hidden from
users but directly accessible from the build system. The library from
make-libstdc++ has missing symbols compared to the one from gcc:lib. The
addition of libgccjit seems to also be unneeded from this change and increases
the closure of e.g. signal-desktop by nearly 10% or 200 MiB.
Fixes#276 and #279.
* nonguix/build-system/chromium-binary.scm (lower)[host-inputs]: Use gcc:lib
again and remove libgccjit.