package/bpftool: needs __sync_*_4 intrisics

bpftool needs __sync_*_4 intrisics since its addition in commit
3675131e6c654d7536a184db0184fde7a97040e0 and
https://github.com/libbpf/libbpf/commit/b0c3d7133faa55fbcbc19f76f9cc9e183e178c97:

/nvmedata/autobuild/instance-26/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/10.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: /nvmedata/autobuild/instance-26/output-1/build/bpftool-v6.7.0/src/libbpf/libbpf.a(libbpf.o): in function `bpf_program__attach_kprobe_opts':
libbpf.c:(.text+0xff88): undefined reference to `__sync_fetch_and_add_4'

Fixes:
 - http://autobuild.buildroot.org/results/919b8351d3783ca30a860df87ae814d5c4b9fd41

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

package/bpftool/Config.in

@@ -10,6 +10,7 @@ config BR2_PACKAGE_BPFTOOL_ARCH_SUPPORTS
 config BR2_PACKAGE_BPFTOOL
 	bool "bpftool"
 	depends on BR2_PACKAGE_BPFTOOL_ARCH_SUPPORTS
+	depends on BR2_TOOLCHAIN_HAS_SYNC_4
 	depends on !BR2_nios2 # binutils
 	depends on BR2_USE_WCHAR # binutils, elfutils
 	depends on !BR2_STATIC_LIBS # elfutils
@@ -24,6 +25,7 @@ config BR2_PACKAGE_BPFTOOL
 
 comment "bpftool needs a uClibc or glibc toolchain w/ wchar, dynamic library, threads, headers >= 4.12"
 	depends on BR2_PACKAGE_BPFTOOL_ARCH_SUPPORTS
+	depends on BR2_TOOLCHAIN_HAS_SYNC_4
 	depends on !BR2_nios2
 	depends on !BR2_USE_WCHAR || BR2_STATIC_LIBS \
 		|| !BR2_TOOLCHAIN_HAS_THREADS \