Replace the entire environment of processes launched from this launcher with the given 'environ' variable.
Typically you will build this variable by using list_variables to copy the process 'environ' and using the functions set_variable, unset_variable, etc.
As an alternative, you can use setenv, unsetenv, etc.
All strings in this array are expected to be in the GLib file name encoding. On UNIX, this means that they can be arbitrary byte strings. On Windows, they should be in UTF-8.
| this | |
| env |
the replacement environment |