PATH_MAX is defined in <limits.h>

--- chuck-1.3.5.2/src/core/util_serial.cpp	2015-10-21 11:04:45.000000000 +0200
+++ chuck-1.3.5.2/src/core/util_serial.cpp	2015-10-25 15:57:34.953700938 +0100
@@ -118,6 +118,7 @@
 #elif defined(__PLATFORM_LINUX__)
 
 
+#include <limits.h>
 #include <sys/types.h>
 #include <dirent.h>
 #include <unistd.h>