package/rng-tools: needs threads

Since the bump to 6.7 there is a new dependency on threads:

https://github.com/nhorman/rng-tools/commit/6952b8ae4736a9b8f58fd2ff330a423ea76cf515

Fixes:
http://autobuild.buildroot.net/results/fff63dd9a53eafe0234ad19f715f050527afedc8/

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rng-tools/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_RNG_TOOLS
 	bool "rng-tools"
 	depends on BR2_PACKAGE_LIBGPG_ERROR_ARCH_SUPPORTS || !(BR2_i386 || BR2_x86_64) # libgcrypt
+	depends on BR2_TOOLCHAIN_HAS_THREADS
 	select BR2_PACKAGE_ARGP_STANDALONE if BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_MUSL
 	select BR2_PACKAGE_JITTERENTROPY_LIBRARY
 	# For rdrand ligcrypt is required and it's not obvious to users
@@ -10,3 +11,6 @@ config BR2_PACKAGE_RNG_TOOLS
 	  Daemon to use hardware random number generators.
 
 	  http://sourceforge.net/projects/gkernel/
+
+comment "rng-tools needs a toolchain w/ threads"
+	depends on !BR2_TOOLCHAIN_HAS_THREADS