package/libbpf: needs headers >= 4.13

Since its addition in commit f7b8508e4fe9c96bf679cc5423cc1500b6523e83,
libbpf unconditionally uses TCA_BPF_ID which is only available since
kernel 4.13 and
https://github.com/torvalds/linux/commit/e86283071fb0eed28136adb52997888f4beb202b:

netlink.c: In function '__get_tc_info':
netlink.c:515:11: error: 'TCA_BPF_ID' undeclared (first use in this function); did you mean 'TCA_BPF_FD'?
  515 |  if (!tbb[TCA_BPF_ID])
      |           ^~~~~~~~~~
      |           TCA_BPF_FD

Fixes:
 - http://autobuild.buildroot.org/results/14996a0b7b9b65d0d6d5717d6da8922752789749

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/libbpf/Config.in

@@ -13,6 +13,7 @@ config BR2_PACKAGE_LIBBPF
 	depends on BR2_USE_WCHAR # elfutils
 	depends on !BR2_STATIC_LIBS # elfutils
 	depends on BR2_TOOLCHAIN_HAS_THREADS # elfutils
+	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_13
 	depends on BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC # elfutils
 	select BR2_PACKAGE_ELFUTILS
 	select BR2_PACKAGE_ZLIB
@@ -24,8 +25,9 @@ config BR2_PACKAGE_LIBBPF
 
 	  https://github.com/libbpf/libbpf
 
-comment "libbpf needs a uClibc or glibc toolchain w/ wchar, dynamic library, threads"
+comment "libbpf needs a uClibc or glibc toolchain w/ wchar, dynamic library, threads, headers >= 4.13"
 	depends on BR2_PACKAGE_LIBBPF_ARCH_SUPPORTS
 	depends on !BR2_USE_WCHAR || BR2_STATIC_LIBS \
 		|| !BR2_TOOLCHAIN_HAS_THREADS \
+		|| !BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_13 \
 		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC)