Long Wine init times since update to Proton 5.0

Hi. I've noticed that Proton 5.0 take very long time to initialize. I wrote a small wrapper script to run different versions of Proton's Wine:

#!/bin/bash
_VERS="$1"
_GAME="$1test"
_STEAMDIR="/home/magist3r/.local/share/Steam/"
PATH="$_STEAMDIR/steamapps/common/Proton $_VERS/dist/bin/:$_STEAMDIR/ubuntu12_32/steam-runtime/amd64/bin:$_STEAMDIR/ubuntu12_32/steam-runtime/amd64/usr/bin:/home/magist3r/.cargo/bin:/home/magist3r/bin:/usr/local/bin:/usr/bin:/bin:/usr/lib/mit/sbin" \
	TERM="xterm" \
	WINEDEBUG="-all" \
	WINEDLLPATH="$_STEAMDIR/steamapps/common/Proton $_VERS/dist/lib64/wine:$_STEAMDIR/steamapps/common/Proton $_VERS/dist/lib/wine" \
	LD_LIBRARY_PATH="$_STEAMDIR/steamapps/common/Proton $_VERS/dist/lib64:$_STEAMDIR/steamapps/common/Proton $_VERS/dist/lib:$_STEAMDIR/ubuntu12_32/steam-runtime/pinned_libs_32:$_STEAMDIR/ubuntu12_32/steam-runtime/pinned_libs_64:/usr/local/lib64:/usr/local/lib:/usr/lib64/graphviz:/lib:/lib64:/usr/lib:/usr/lib64:/usr/lib/tls:/usr/lib64/tls:$_STEAMDIR/ubuntu12_32/steam-runtime/i386/lib/i386-linux-gnu:$_STEAMDIR/ubuntu12_32/steam-runtime/i386/lib:$_STEAMDIR/ubuntu12_32/steam-runtime/i386/usr/lib/i386-linux-gnu:$_STEAMDIR/ubuntu12_32/steam-runtime/i386/usr/lib:$_STEAMDIR/ubuntu12_32/steam-runtime/amd64/lib/x86_64-linux-gnu:$_STEAMDIR/ubuntu12_32/steam-runtime/amd64/lib:$_STEAMDIR/ubuntu12_32/steam-runtime/amd64/usr/lib/x86_64-linux-gnu:$_STEAMDIR/ubuntu12_32/steam-runtime/amd64/usr/lib:" \
	WINEPREFIX="$_STEAMDIR/steamapps/compatdata/$_GAME/" \
	WINEESYNC="1" \
	SteamGameId="$_GAME" \
	SteamAppId="$_GAME" \
	WINEDLLOVERRIDES="steam.exe=b;d3d11=n;d3d10=n;d3d10core=n;d3d10_1=n;dxgi=n" \
	STEAM_COMPAT_CLIENT_INSTALL_PATH="$_STEAMDIR" \
	WINE="$_STEAMDIR/steamapps/common/Proton $_VERS/dist/bin/wine" "$_STEAMDIR/steamapps/common/Proton $_VERS/dist/bin/wine" "$2"

And then issued two commands. For Proton 4.11:

time ./proton-wrapper.sh 4.11 wineboot
wine: created the configuration directory '/home/magist3r/.local/share/Steam//steamapps/compatdata/4.11test'
esync: up and running.
wine: configuration in '/home/magist3r/.local/share/Steam//steamapps/compatdata/4.11test' has been updated.

real    0m4,060s
user    0m0,011s
sys     0m0,009s

And for Proton 5.0:

time ./proton-wrapper.sh 5.0 wineboot
wine: created the configuration directory '/home/magist3r/.local/share/Steam//steamapps/compatdata/5.0test'
esync: up and running.
wine: configuration in L"/home/magist3r/.local/share/Steam//steamapps/compatdata/5.0test" has been updated.

real    0m27,873s
user    0m0,012s
sys     0m0,011s

As you can see, there is a huge difference. As a result I have to wait for minutes to launch a game with Proton 5.0.

Start with the provided ./proton-wrapper.sh entry point and reproduce the wineboot timings for Proton 4.11 and 5.0. Compare the initialization behavior and review the 11-comment discussion for any established direction. Done means identifying the Proton 5.0 startup regression and verifying a measurable improvement in initialization time.