kexec-tools: fix build error with glibc 2.19 and earlier version

[Simon Horman]

On Sat, Oct 03, 2015 at 02:38:22PM +0800, Dave Young wrote:
> kexec-tools build fails on my laptop with RHEL7.1 installed:
>   gcc -g -O2 -fno-strict-aliasing -Wall -Wstrict-prototypes -I./include -I./util_lib/include -Iinclude/  -I./kexec/arch/x86_64/include  -c -MD -o kexec/arch/i386/kexec-x86-common.o kexec/arch/i386/kexec-x86-common.c
>   In file included from kexec/arch/i386/kexec-x86-common.c:36:0:
>   kexec/arch/i386/../../kexec.h:19:2: error: #error BYTE_ORDER not defined
>    #error BYTE_ORDER not defined
>     ^
>   kexec/arch/i386/../../kexec.h:23:2: error: #error LITTLE_ENDIAN not defined
>    #error LITTLE_ENDIAN not defined
>     ^
>   kexec/arch/i386/../../kexec.h:27:2: error: #error BIG_ENDIAN not defined
>    #error BIG_ENDIAN not defined
>     ^
>   In file included from kexec/arch/i386/kexec-x86-common.c:37:0:
>   kexec/arch/i386/../../kexec-syscall.h: In function ‘kexec_load’:
>   kexec/arch/i386/../../kexec-syscall.h:74:2: warning: implicit declaration of function ‘syscall’ [-Wimplicit-function-declaration]
>     return (long) syscall(__NR_kexec_load, entry, nr_segments, segments, flags);
>     ^
>   make: *** [kexec/arch/i386/kexec-x86-common.o] Error 1
> 
> The build error was introduced by below commit:
> 
>   commit c9c21cc107dcc9b6053e39ead1069e03717513f9
>   Author: Baoquan He <bhe at redhat.com>
>   Date:   Thu Aug 6 19:10:55 2015 +0800
> 
>       kexec: use _DEFAULT_SOURCE instead to remove compiling warning
> 
>       Now compiling will print warning like below. Change code as it suggested.
>        # warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
>          ^
> 
> See manpage: http://man7.org/linux/man-pages/man7/feature_test_macros.7.html
> 
> _BSD_SOURCE has been deprecated since glibc 2.20, To allow code that requires
> _BSD_SOURCE in glibc 2.19 and earlier and _DEFAULT_SOURCE in glibc 2.20 and
> later to compile without warnings, define both _BSD_SOURCE and _DEFAULT_SOURCE.
> 
> Thus fix it by adding back _BSD_SOURCE along with _DEFAULT_SOURCE.
> 
> Signed-off-by: Dave Young <dyoung at redhat.com>

Thanks Dave,

applied.