libtorrent: disable on ARC arch

Libtorrent has dependencies on atomic operations. However ARC GCC doesn't
implement those at the moment so package should be disabled. Rtorrent
depends on libtorrent.

This fixes:
http://autobuild.buildroot.net/results/51414e22c8ea47c38df20d864526a370c5a895d7/

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libtorrent/Config.in

@@ -2,6 +2,8 @@ config BR2_PACKAGE_LIBTORRENT
 	bool "libtorrent"
 	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_TOOLCHAIN_HAS_THREADS
+	# ARC GCC doesn't support atomic instructions required by this lib
+	depends on !BR2_arc
 	select BR2_PACKAGE_LIBSIGC
 	help
 	  BitTorrent library written in C++ for *nix
@@ -10,3 +12,4 @@ config BR2_PACKAGE_LIBTORRENT
 
 comment "libtorrent needs a toolchain w/ C++, threads"
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS
+	depends on !BR2_arc

package/rtorrent/Config.in

@@ -4,6 +4,8 @@ config BR2_PACKAGE_RTORRENT
 	depends on BR2_USE_WCHAR
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_USE_MMU # fork()
+	# ARC GCC doesn't support atomic instructions required by libtorrent
+	depends on !BR2_arc
 	select BR2_PACKAGE_LIBCURL
 	select BR2_PACKAGE_LIBSIGC
 	select BR2_PACKAGE_LIBTORRENT
@@ -17,3 +19,4 @@ config BR2_PACKAGE_RTORRENT
 comment "rtorrent needs a toolchain w/ C++, threads, wchar"
 	depends on BR2_USE_MMU
 	depends on !(BR2_INSTALL_LIBSTDCPP && BR2_USE_WCHAR && BR2_TOOLCHAIN_HAS_THREADS)
+	depends on !BR2_arc