Bare compile: support multiple paths wildcards.

Similarly to PATH env variable, this allows to pass paths to bare
compiler which do not fit nicely into a single wildcard structure.
Colon (":") is used as separator.

This provides more flexibility when rebar is run in offline/hermetic
environment, e.g. #958 and #1281.

src/rebar_prv_bare_compile.erl

@@ -29,7 +29,8 @@ init(State) ->
                                                   {example, ""},
                                                   {short_desc, ""},
                                                   {desc, ""},
-                                                  {opts, [{paths, $p, "paths", string, "Wildcard path of ebin directories to add to code path"}]}])),
+                                                  {opts, [{paths, $p, "paths", string, "Wildcard paths of ebin directories to add to code path, separated by a colon"},
+                                                          {separator, $s, "separator", string, "In case of multiple return paths, the separator character to use to join them."}]}])),
     {ok, State1}.
 
 -spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
@@ -39,8 +40,9 @@ do(State) ->
     %% Add code paths from --paths to the beginning of the code path
     {RawOpts, _} = rebar_state:command_parsed_args(State),
     Paths = proplists:get_value(paths, RawOpts),
-    CodePaths = filelib:wildcard(Paths),
-    code:add_pathsa(CodePaths),
+    Sep = proplists:get_value(separator, RawOpts, " "),
+    [ code:add_pathsa(filelib:wildcard(PathWildcard))
+      || PathWildcard <- string:tokens(Paths, Sep) ],
 
     [AppInfo] = rebar_state:project_apps(State),
     AppInfo1 = rebar_app_info:out_dir(AppInfo, rebar_dir:get_cwd()),