package/alljoyn: needs BR2_TOOLCHAIN_HAS_SYNC_4

After applying a patch like [1], the build failed with the following
error:
liballjoyn_c.a(Message.o): In function `alljoyn_message_destroy':
Message.cc:(.text+0x74): undefined reference to `__sync_sub_and_fetch_4'
liballjoyn.so: undefined reference to `__sync_bool_compare_and_swap_4'
liballjoyn.so: undefined reference to `__sync_add_and_fetch_4'

So, add dependency on BR2_TOOLCHAIN_HAS_SYNC_4 which also disable the
alljoyn build on sparc.

[1] https://git.buildroot.org/buildroot/commit/?id=c5e96d8935016456bea342db170ae6a139a8470f

Fixes:
http://autobuild.buildroot.net/results/cea/cea62a7ed7f1eda6f817d8e27fd645942def25ec

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/alljoyn/Config.in

@@ -3,6 +3,7 @@ config BR2_PACKAGE_ALLJOYN
 	depends on BR2_USE_MMU # fork()
 	depends on !BR2_STATIC_LIBS
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_TOOLCHAIN_HAS_SYNC_4
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_USE_WCHAR
 	select BR2_PACKAGE_LIBCAP
@@ -19,5 +20,6 @@ config BR2_PACKAGE_ALLJOYN
 
 comment "alljoyn needs a toolchain w/ C++, threads, wchar and dynamic library"
 	depends on BR2_USE_MMU
+	depends on BR2_TOOLCHAIN_HAS_SYNC_4
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS || \
 		!BR2_USE_WCHAR || BR2_STATIC_LIBS