silence -Wstring-truncation for correct use of strncpy (#5146)

- ensuring header is zerod

firmware/console/binary_log/log_field.cpp

@@ -43,10 +43,13 @@ void LogField::writeHeader(Writer& outBuffer) const {
 	buffer[54] = m_digits;
 
 	// Offset 55, (optional) category string
+	memset(&buffer[55], 0, 34);
 	if (m_category) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstringop-truncation"
+		// strncpy's exclusion of null terminator is correct and appropriate behavior for this field
 		strncpy(&buffer[55], m_category, 34);
-	} else {
-		memset(&buffer[55], 0, 34);
+#pragma GCC diagnostic pop
 	}
 
 	// Total size = 89