buildgcc: Update to gdb 8.0 and expat 2.2.1

Among other improvements, the new GDB has a new GDB/CLI
command to erase flash memory and a few Python scripting
enhancements.

Change-Id: Ie3852d5bc74617d3e05509e19bbd1caa281da3e0
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/20799
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>

util/crossgcc/patches/gdb-8.0_pythonhome.patch

@@ -0,0 +1,19 @@
+diff -urN gdb-8.0.orig/gdb/python/python.c gdb-8.0/gdb/python/python.c
+--- gdb-8.0.orig/gdb/python/python.c	2016-02-09 19:19:39.000000000 -0800
++++ gdb-8.0/gdb/python/python.c	2016-04-21 17:45:39.119833428 -0700
+@@ -1748,6 +1748,15 @@
+ #endif
+ #endif
+ 
++  char readlinkbuffer[BUFSIZ];
++  int readlinks = readlink("/proc/self/exe", readlinkbuffer, BUFSIZ - 1);
++  readlinkbuffer[readlinks] = 0;
++  char *executeablepath = dirname(readlinkbuffer);
++  char *pythonhome = malloc(strlen(executeablepath) + strlen("/../") + 2);
++  strcpy(pythonhome, executeablepath);
++  strcat(pythonhome, "/../");
++  setenv("PYTHONHOME", pythonhome, 1);
++
+   Py_Initialize ();
+   PyEval_InitThreads ();
+