[log] add build option OT_LOG_MAX_SIZE to set the max log string size (#10948)

examples/platforms/simulation/logging.c

@@ -101,7 +101,7 @@ void otPlatLog(otLogLevel aLogLevel, otLogRegion aLogRegion, const char *aFormat
 
     if (sLogFile == NULL)
     {
-        char logString[512];
+        char logString[12 /* NodeId */ + OPENTHREAD_CONFIG_LOG_MAX_SIZE];
         int  offset;
 
         offset = snprintf(logString, sizeof(logString), "[%lu]", (unsigned long)gNodeId);

examples/platforms/utils/logging_rtt.h

@@ -93,7 +93,8 @@ extern "C" {
  * stack.
  */
 #ifndef LOG_PARSE_BUFFER_SIZE
-#define LOG_PARSE_BUFFER_SIZE 128
+#define LOG_PARSE_BUFFER_SIZE \
+    (19 /* Timestamp */ + 8 /* RTT color code */ + OPENTHREAD_CONFIG_LOG_MAX_SIZE + 1 /* \n */)
 #endif
 
 /**