build: convert debug to Kconfig

Enabling debug will disable NDEBUG which will result in more debug
prints.  There are a number of debugging options for Xen so place the
debug option under a menu for different debugging options to have a way
to group them all together.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/Kconfig

@@ -26,3 +26,5 @@ config DEFCONFIG_LIST
 config EXPERT
 	string
 	option env="XEN_CONFIG_EXPERT"
+
+source "Kconfig.debug"

xen/Kconfig.debug

@@ -0,0 +1,14 @@
+
+menu "Debugging Options"
+
+config DEBUG
+	bool "Developer Checks"
+	default y
+	---help---
+	  If you say Y here this will enable developer checks such as asserts
+	  and extra printks. This option is intended for development purposes
+	  only, and not for production use.
+
+	  You probably want to say 'N' here.
+
+endmenu

xen/Rules.mk

@@ -20,13 +20,14 @@ include $(XEN_ROOT)/Config.mk
 ifeq ($(debug),y)
 verbose       := y
 frame_pointer := y
-else
-CFLAGS += -DNDEBUG
 endif
 ifeq ($(perfc_arrays),y)
 perfc := y
 endif
 
+ifeq ($(origin debug),command line)
+$(warning "You must use 'make menuconfig' to enable/disable debug now.")
+endif
 ifneq ($(origin kexec),undefined)
 $(error "You must use 'make menuconfig' to enable/disable kexec now.")
 endif

xen/include/xen/config.h

@@ -81,4 +81,8 @@
 /* allow existing code to work with Kconfig variable */
 #define NR_CPUS CONFIG_NR_CPUS
 
+#ifndef CONFIG_DEBUG
+#define NDEBUG
+#endif
+
 #endif /* __XEN_CONFIG_H__ */