nonguix: chromium-binary-build-system: Use gcc:lib.

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.

nonguix/build-system/chromium-binary.scm

@@ -83,11 +83,10 @@
       ("expat" ,expat)
       ("fontconfig" ,fontconfig)
       ("freetype" ,freetype)
-      ("gcc:lib" ,(make-libstdc++ gcc))
+      ("gcc:lib" ,gcc "lib")
       ("glib" ,glib)
       ("gtk+" ,gtk+)
       ("libdrm" ,libdrm)
-      ("libgccjit" ,libgccjit)
       ("libnotify" ,libnotify)
       ("librsvg" ,librsvg)
       ("libsecret" ,libsecret)