qt: Webkit Module needs a toolchain with NPTL

Qt Webkit Module uses pthread_getattr_np() which is implemented in
toolchains with NPTL. Otherwise the compilation will fail showing this
error message:

wtf/StackBounds.cpp: In member function ‘void
WTF::StackBounds::initialize()’:
wtf/StackBounds.cpp:172:38: error: ‘pthread_getattr_np’ was not declared
in this scope

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qt/Config.in

@@ -375,12 +375,14 @@ config BR2_PACKAGE_QT_WEBKIT
 	depends on BR2_PACKAGE_QT_GUI_MODULE
 	depends on BR2_PACKAGE_QT_NETWORK
 	depends on BR2_PACKAGE_QT_ARCH_SUPPORTS_WEBKIT
+	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL # needs pthread_getattr_np()
 	help
 	  Build the WebKit module.
 	  If unsure, say n.
 
-comment "WebKit needs shared library/gui/network support"
+comment "WebKit needs shared library/NPTL toolchain/gui/network support"
 	depends on !(BR2_PACKAGE_QT_SHARED && BR2_PACKAGE_QT_GUI_MODULE && BR2_PACKAGE_QT_NETWORK)
+	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL
 	depends on BR2_PACKAGE_QT_ARCH_SUPPORTS_WEBKIT
 
 config BR2_PACKAGE_QT_STL