sandbox: Adjust Makefile so that standalone/api are not built

The check for sandbox architecture is too early in the Makefile, so
standalone and api are built regardless. This moves the check until
after autoconf.mk has been read.

This fixes a build breakage.
Signed-off-by: NSimon Glass <sjg@chromium.org>

Makefile

@@ -142,9 +142,6 @@ unexport CDPATH
 SUBDIR_TOOLS = tools
 SUBDIR_EXAMPLES = examples/standalone examples/api
 SUBDIRS = $(SUBDIR_TOOLS)
-ifndef CONFIG_SANDBOX
-SUBDIRS += $(SUBDIR_EXAMPLES)
-endif
 
 .PHONY : $(SUBDIRS) $(VERSION_FILE) $(TIMESTAMP_FILE)
 
@@ -157,6 +154,10 @@ all:
 sinclude $(obj)include/autoconf.mk.dep
 sinclude $(obj)include/autoconf.mk
 
+ifndef CONFIG_SANDBOX
+SUBDIRS += $(SUBDIR_EXAMPLES)
+endif
+
 # load ARCH, BOARD, and CPU configuration
 include $(obj)include/config.mk
 export	ARCH CPU BOARD VENDOR SOC