How files are searched and loaded by ARC (ARgile Compiler)
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When loading a shared object module with `--shared-module' or environment
variable `ARGILE_SO_MODULES' (or when the default std module is loaded),
the file with extension `.so' is searched in directories
listed in `ARGILE_SOM_PATH' environment variable.
If ARGILE_SOM_PATH is not set, the `/argile/' subdirectory of all entries
in LD_LIBRARY_PATH are searched, as well as /usr/lib/argile ,
$HOME/lib/argile/ and the current directory.

When loading an Argile file, it is searched in directories listed in
environment variable `ARGILE_FILE_PATH' and `--add-dir' command
line option. It is searched with extension `.argl' then `.arg' then without
additional extension. Argile files maybe loaded when the `std/use' binding is
called, or they can be preloaded with `--use' command line option or with
the `ARGILE_AUTO_USE' environment variable.
If ARGILE_FILE_PATH is not set, the `/argile/' subdirectory of all entries
in LD_LIBRARY_PATH are searched, as well as /usr/lib/argile ,
$HOME/lib/argile/ and the current directory.
