[core/os] get_current_directory: Add allocator arg to targets where its missing

core/os/os_openbsd.odin

@@ -806,7 +806,7 @@ get_env :: proc(key: string, allocator := context.allocator) -> (value: string)
 }
 
 @(require_results)
-get_current_directory :: proc() -> string {
+get_current_directory :: proc(allocator := context.allocator) -> string {
 	buf := make([dynamic]u8, MAX_PATH)
 	for {
 		cwd := _unix_getcwd(cstring(raw_data(buf)), c.size_t(len(buf)))