tor: needs thread support

Fixes:

  http://autobuild.buildroot.org/results/4f7/4f758978f6820ecceaad57385f3c104011180c4d/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/tor/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_TOR
 	bool "tor"
 	depends on BR2_USE_MMU # fork()
+	depends on BR2_TOOLCHAIN_HAS_THREADS
 	select BR2_PACKAGE_LIBEVENT
 	select BR2_PACKAGE_OPENSSL
 	select BR2_PACKAGE_ZLIB
@@ -12,3 +13,7 @@ config BR2_PACKAGE_TOR
 	  state security.
 
 	  https://www.torproject.org
+
+comment "tor needs a toolchain w/ threads"
+	depends on BR2_USE_MMU
+	depends on !BR2_TOOLCHAIN_HAS_THREADS