[posix-app] log filename when die (#4155)

This commit aims at adding the filename when die.

Other enhancements:
- Enable PLATFORM region by default for posix-app
- Disable warning for zero variadic macro arguments
- Use VerifyOrExit to implement other assert utilities
- Do not call fprintf() and print exit code in assert utility

To print dying message to stderr, add -v when launching the app.
To get the exit code, use echo $? just after the app died.

tests/unit/test_hdlc.cpp

@@ -517,7 +517,7 @@ void TestEncoderDecoder(void)
 
 uint32_t GetRandom(uint32_t max)
 {
-    return rand() % max;
+    return static_cast<uint32_t>(rand()) % max;
 }
 
 void TestFuzzEncoderDecoder(void)