Bugfixes and reactors for install-vrcx.sh

[regalialong]

I apologize for doing this in a single commit but we're past the point to fix this now.

This PR fixes #841 by switching to using the wine binary and instead asking per WINEARCH to use 64bit, which should be more consistent across distros.
This PR also fixes #853 which describes two separate issues:

• We now delete the application folder's contents if it exists, which prevents the install script from failing on unzip. This behavior seems to be consistent with what the graphical installer does as well.
• The script now exports WINEDLLOVERRIDES as described in this Wine bug report as workaround for a blackscreen issue.

I've took the opportunity to also clean up some stuff, the script now:

• uses $HOME consistently instead of switching between ~ and $HOME
• uses $XDG_DATA_HOME, which signals that the user has an alternative preferred path for what otherwise defaults to $HOME/.local/share
  • This as a byproduct makes the script now use $WINEPREFIX consistently
  • A snag is that the XDG Base Directory Specification signals no way to override $HOME/.local/bin, so we just have to use it as-is.
• uses ln -nsf to override the symbolic link we do to install the vrcx binary wrapper script into $HOME/.local/bin.
  • The most recent install is likely going to be the most relevant, users who need multiple installations will know what to do.
• uses set -u to bail on unset variables, which adds guard rails for when this script inevitably trips

Wine automatically creates $XDG_DATA_HOME/applications and $XDG_DATA_HOME/icons if it doesn't exist to populate it with its own files, which allows me to shave off the checks for the directories.