feat: add ability to pass user flags to python interpreter

Author: muravev-vasilii

Diff for: py/private/run.tmpl.sh

@@ -58,4 +58,5 @@ if [ -n "${BASH:-}" -o -n "${ZSH_VERSION:-}" ] ; then
     hash -r 2> /dev/null
 fi
 
-exec "{{EXEC_PYTHON_BIN}}" {{INTERPRETER_FLAGS}} "$(rlocation {{ENTRYPOINT}})" "$@"
+RULES_PY_USER_INTERPRETER_FLAGS="${RULES_PY_USER_INTERPRETER_FLAGS:-}"
+exec "{{EXEC_PYTHON_BIN}}" {{INTERPRETER_FLAGS}} $RULES_PY_USER_INTERPRETER_FLAGS "$(rlocation {{ENTRYPOINT}})" "$@"