adapted path for GDBMACROS in pintos-gdb. the environment variable

PINTOSPATH should always point to the pintos src folder

src/utils/pintos-gdb

 #! /bin/sh
 
-# Path to GDB macros file.  Customize for your site.
-GDBMACROS=/usr/class/cs140/pintos/pintos/src/misc/gdb-macros
+# Path to GDB macros file.
+GDBMACROS="$PINTOSPATH/misc/gdb-macros"
 
 # Choose correct GDB.
 if command -v i386-elf-gdb >/dev/null 2>&1; then
@@ -16,5 +16,7 @@ if test -f "$GDBMACROS"; then
 else
 	echo "*** $GDBMACROS does not exist ***"
 	echo "*** Pintos GDB macros will not be available ***"
+  echo "*** The environment variable \$PINTOSPATH should to point"
+  echo "    to your location of the pintos src folder ***"
 	exec $GDB "$@"
 fi