package/libseccomp: needs headers >= 3.12

EM_AARCH64 was added to linux kernel with version 3.12:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/log/include/uapi/linux/elf-em.h?h=linux-3.12.y

Fixes
http://autobuild.buildroot.net/results/4cd/4cd6aaccde9fb0f80e49133b477f330b601f4a63/
http://autobuild.buildroot.net/results/bd1/bd105e821de583e582199aae31fab13ef17e67a0/
http://autobuild.buildroot.net/results/092/092143df2b91d50850067274da531c713f2ccb72/
http://autobuild.buildroot.net/results/814/8149cf0c3ef3ef8d91b5891591a71691dc3d7427/

[Thomas: fix Config.in comment.]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libseccomp/Config.in

@@ -2,6 +2,7 @@ config BR2_PACKAGE_LIBSECCOMP
 	bool "libseccomp"
 	depends on BR2_aarch64 || BR2_mips || BR2_mipsel || BR2_mips64 || \
 		BR2_mips64el || BR2_i386 || BR2_x86_64
+	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_12
 	help
 	  High level interface to the Linux Kernel's seccomp filter
 
@@ -13,3 +14,8 @@ config BR2_PACKAGE_LIBSECCOMP
 	  and easily adopted by application developers.
 
 	  https://github.com/seccomp/libseccomp
+
+comment "libseccomp needs a toolchain w/ headers >= 3.12"
+	depends on BR2_aarch64 || BR2_mips || BR2_mipsel || BR2_mips64 || \
+		BR2_mips64el || BR2_i386 || BR2_x86_64
+	depends on !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_12