AppImage: Set OPENSSL_CONF for newer openssl compat (#3283)

On systems with newer versions of openssl, the installed file
/etc/ssl/openssl.cnf is incompatible with our bundled version of
libssl.so, but will be loaded by default unless OPENSSL_CONF is
set to /dev/null (or some other invalid path) in the environment.

Author: ferdnyc

installer/launch-linux.sh

@@ -3,9 +3,14 @@
 # Add the current folder the library path
 LD_LIBRARY_PATH="."
 
-# Set some environment variables for ImageMagick and Qt5
+# Set some environment variables
 export QT_PLUGIN_PATH="."
 
+# For Debian-based systems with newer openssl, see:
+# https://github.com/OpenShot/openshot-qt/issues/3242
+# https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=918727 
+export OPENSSL_CONF=/dev/null
+
 # Launch application
 HERE="$(dirname "$(readlink -f "${0}")")"
 exec "${HERE}"/openshot-qt "$@"