kernel: build bin2c based on config option CONFIG_BUILD_BIN2C

currently bin2c builds only if CONFIG_IKCONFIG=y. But bin2c will now be
used by kexec too.  So make it compilation dependent on CONFIG_BUILD_BIN2C
and this config option can be selected by CONFIG_KEXEC and CONFIG_IKCONFIG.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: WANG Chao <chaowang@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/Kconfig

@@ -1582,6 +1582,7 @@ source kernel/Kconfig.hz
 
 config KEXEC
 	bool "kexec system call"
+	select BUILD_BIN2C
 	---help---
 	  kexec is a system call that implements the ability to shutdown your
 	  current kernel, and to start another kernel.  It is like a reboot

init/Kconfig

@@ -783,8 +783,13 @@ endchoice
 
 endmenu # "RCU Subsystem"
 
+config BUILD_BIN2C
+	bool
+	default n
+
 config IKCONFIG
 	tristate "Kernel .config support"
+	select BUILD_BIN2C
 	---help---
 	  This option enables the complete Linux kernel ".config" file
 	  contents to be saved in the kernel. It provides documentation

scripts/basic/Makefile

@@ -9,7 +9,7 @@
 # fixdep: 	 Used to generate dependency information during build process
 
 hostprogs-y	:= fixdep
-hostprogs-$(CONFIG_IKCONFIG)     += bin2c
+hostprogs-$(CONFIG_BUILD_BIN2C)     += bin2c
 always		:= $(hostprogs-y)
 
 # fixdep is needed to compile other host programs