global: Use CONFIG_XPL_BUILD instead of CONFIG_SPL_BUILD

Complete this rename for all directories outside arch/ board/ drivers/
and include/

Use the new symbol to refer to any 'SPL' build, including TPL and VPL

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/lib/Makefile b/test/lib/Makefile
index 70f14c4..a54387a 100644
--- a/test/lib/Makefile
+++ b/test/lib/Makefile
@@ -2,7 +2,7 @@
 #
 # (C) Copyright 2018
 # Mario Six, Guntermann & Drunck GmbH, mario.six@gdsys.cc
-ifeq ($(CONFIG_SPL_BUILD),)
+ifeq ($(CONFIG_XPL_BUILD),)
 obj-y += cmd_ut_lib.o
 obj-y += abuf.o
 obj-y += alist.o