Turns out, zoom couldn't launch QtWebEngineProcess because of wrong interpreter
Also, there was a need for some extra deps, which I found when
running debug version of zoom.
* paxmark zoom to fix execution on PaX-enabled kernels[1]
* Requires moving from qt55 to qt56
* Put libs as buildInputs so that wrapQtProgram sees their paths!
* Don't use bundled Qt libs.
(if these should be used, we shouldn't put our own on rpath, etc.)
[1] Without this, program fails to start (but doesn't exit),
and the following exception is logged a few times:
Dec 07 12:24:26 hostname kernel: grsec: denied RWX mmap of <anonymous mapping> by /nix/store/v1i2bff9fs7w1vycv0y615phhs7hky87-zoom-us/share/.zoom-wrapped[.zoom-wrapped:23812] uid/euid:1000/1
zoom still won't run unless using a pax-fixed version of qtwebengine.
( see: https://github.com/NixOS/nixpkgs/pull/20991 )
Only zoom-us depends on icu4c-54.1. Since we know that version has some vulnerabilities, and zoom-us appears to work with icu4c-57.1, I remove the icu/54.1.nix file, remove icu_54_1 from all-packages.nix, and have zoom-us depend on icu (i.e., icu4c-57.1)
