Move global Timeout object from utest_shim in static function.

The change of scope allow the linker to remove the variable if not used.

Author: pan-

features/frameworks/utest/source/utest_shim.cpp

@@ -66,7 +66,10 @@ static volatile utest_v1_harness_callback_t minimal_callback;
 static volatile utest_v1_harness_callback_t ticker_callback;
 
 // Timeout object used to control the scheduling of test case callbacks
-Timeout utest_timeout_object;
+static Timeout& utest_timeout_object() {
+    static Timeout timeout;
+    return timeout;
+}
 
 static void ticker_handler()
 {
@@ -88,7 +91,7 @@ static void *utest_us_ticker_post(const utest_v1_harness_callback_t callback, ti
     if (delay_ms) {
         ticker_callback = callback;
         // fire the interrupt in 1000us * delay_ms
-        utest_timeout_object.attach_us(ticker_handler, delay_us);
+        utest_timeout_object().attach_us(ticker_handler, delay_us);
 
     } 
     else {
@@ -102,7 +105,7 @@ static int32_t utest_us_ticker_cancel(void *handle)
 {
     UTEST_LOG_FUNCTION();
     (void) handle;
-    utest_timeout_object.detach();
+    utest_timeout_object().detach();
     return 0;
 }
 static int32_t utest_us_ticker_run()