znc: add mandatory dependency on threads

Threads support is mandatory since version 1.7.0:
https://github.com/znc/znc/commit/582cd635f5a047761b1052a40088ab86e62fffc1

Fixes:
 - http://autobuild.buildroot.net/results/cc56c7dbee594056288296398772ef9e22846299

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/znc/Config.in

@@ -4,12 +4,13 @@ config BR2_PACKAGE_ZNC
 	depends on BR2_USE_MMU # fork()
 	depends on !BR2_STATIC_LIBS
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
+	depends on BR2_TOOLCHAIN_HAS_THREADS
 	help
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 	  http://www.znc.in
 
-comment "znc needs a toolchain w/ C++, dynamic library, gcc >= 4.8"
+comment "znc needs a toolchain w/ C++, dynamic library, gcc >= 4.8, threads"
 	depends on !BR2_INSTALL_LIBSTDCPP || BR2_STATIC_LIBS || \
-		!BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
+		!BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 || !BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_USE_MMU