package/boost: boost-log needs NPTL threads

Fixes:
[xtensa]
http://autobuild.buildroot.net/results/664/6642dc9c569b2820a9d0e273fc2fb1d5a635ba0a
[arc]
http://autobuild.buildroot.net/results/ba5/ba5836e9a77e1b48e24ace46ca1611c22524261d
[bfin]
http://autobuild.buildroot.net/results/8cd/8cdac9cc67394aaae09ee816a9adddec762e3bd0

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

package/boost/Config.in

@@ -89,6 +89,10 @@ comment "boost-locale needs a toolchain w/ wchar"
 
 config BR2_PACKAGE_BOOST_LOG
 	bool "boost-log"
+	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL
+
+comment "boost-log needs a toolchain w/ NPTL"
+	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL
 
 config BR2_PACKAGE_BOOST_MATH
 	bool "boost-math"