Exit command causing hard fault on Silabs devices (project-chip#42759)

* [SL-UP] MATTER-5715: Exit command causing hard fault (project-chip#779)

* stub exit command and print unsupported msg

* Revert "stub exit command and print unsupported msg"

This reverts commit 8422dec0e70b2e2ebfd44517c6c4fbb6b8e1e095.

* refactor to reset system on exit call

* use sizeof for print

Author: miduggan24

examples/platform/silabs/syscalls_stubs.cpp

@@ -30,6 +30,8 @@
 #include <string.h>
 #include <sys/stat.h>
 
+#include <em_device.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -236,6 +238,24 @@ int __attribute__((weak)) _write(int file, const char * ptr, int len)
 }
 #endif // SILABS_LOG_OUT_UART
 
+/**************************************************************************
+ * @brief
+ *  Override exit to prevent hard fault
+ *
+ * @param[in] status
+ *  Exit status (not used).
+ **************************************************************************/
+void __attribute__((weak)) exit(int status)
+{
+    (void) status;
+    static const char kExitMessage[] = "exit not supported, resetting system...\r\n";
+    _write(0, kExitMessage, sizeof(kExitMessage) - 1);
+    NVIC_SystemReset();
+    while (1)
+    {
+    } // Unreachable, satisfies noreturn attribute
+}
+
 #ifdef __cplusplus
 }
 #endif