Feature/zephyr ztest (#118)

* Leverage (older) embedded unit tests into external unit tests build upon copy of Zephyr's ztest library and CMake.

* Expand top-level CMake build to run external unit tests.

* Expand Zephyr module extension to run external unit tests via west or sanitycheck.

Co-authored-by: Gregory Shue <gregory.shue@legrand.us>

src/bacnet/bacapp.c

@@ -1132,7 +1132,8 @@ int bacapp_snprintf_value(
                                 wc = L'.';
                             }
                         }
-                        snprintf(temp_str, sizeof(temp_str), "%lc", wc);
+                        /* For portability, cast wchar_t to wint_t */
+                        snprintf(temp_str, sizeof(temp_str), "%lc", (wint_t)wc);
                         if (!append_str(&p_str, &rem_str_len, temp_str)) {
                             break;
                         }