attempt flextools compatibility with flatpak

flextools.sh

#!/bin/bash
# Be sure to set execute permission for the script.

# Configure how to call python here:
CALLPYTHON=python

# Configure the prefix to the path where FieldWorks is installed.
# /usr is the default for installing via the apt package manager on Ubuntu:
# /app is the default for flatpak
prefix=/app

# In order to function correctly on Linux,
# we need to source a shell script (environ), which
# erases the path and several other environment variables.
# This function is called after the variables needed by FLEx
# are sourced in order to reset any variables needed by
# the caller which were erased.
resetenviron() {
    echo "Resetting environment"
    # Reset pyenv variables
    export PATH="$HOME/.pyenv/bin:$PATH"
    
    # Try setting path to libc.so.6, etc needed by python installed by pyenv (2.34), 
    # otherwise flatpack only finds its internal version of libc (2.30)
    # However, after setting this, it crashes with "Segmentation fault (core dumped)"
    export LD_LIBRARY_PATH="/var/run/host/usr/lib/x86_64-linux-gnu:$LD_LIBRARY_PATH"
    
    eval "$(pyenv init --path)"
    eval "$(pyenv virtualenv-init -)"
}


# The following is adapted from the run-app shell script
# used to run an installed version of FLEx on Linux.
scriptdir=$(/bin/pwd)
lib=$prefix/lib/fieldworks
share=$prefix/share/fieldworks
sharedWsRoot=/var/lib/fieldworks
sharedWs=$sharedWsRoot/SIL/WritingSystemStore

# "$share/setup-user"

cd "$lib"; RUNMODE="INSTALLED" . environ;
cd $scriptdir

# reset environment as defined above
resetenviron



exec $CALLPYTHON ../scripts/RunFlexTools.py DEBUG

See this issue with PyCharm for related bugs when trying to use pyenv with its flatpak version: flathub/com.jetbrains.PyCharm-Community#14