libdl-sh: Preserve and restore environment
libdl-sh: Preserve and restore environment

Since we can't make assumptions about the command executed by action
'exec', we need to preserve environment variables LC_ALL, GETOPT_-
COMPATIBLE, and POSIXLY_CORRECT (as they get modfied for command line
processing with getopt(1)) and restore them before command execution.

donkarlos/libdl-sh