onlyoffice-bin: add gcc lib to runtimeInputs

OnlyOffice is currently not launching
(https://github.com/NixOS/nixpkgs/issues/218238), due to a missing
library (libstdc++.so.6).

I used nix-locate to see which outputs provide it, and
`gcc-unwrapped.lib` is the one that makes more sense to me, but I'm not
sure if there's a better way to supply that lib.

pkgs/applications/office/onlyoffice-bin/default.nix

@@ -12,6 +12,7 @@
 , dconf
 , dpkg
 , fontconfig
+, gcc-unwrapped
 , gdk-pixbuf
 , glib
 , glibc
@@ -66,6 +67,7 @@ let
   runtimeLibs = lib.makeLibraryPath [
     curl
     glibc
+    gcc-unwrapped.lib
     libudev0-shim
     pulseaudio
   ];