libdrm: needs threads

libdrm select libpthread-stubs that needs threads support.

Fixes:
http://autobuild.buildroot.net/results/1da/1dad13110312a44b40b9ee4050b265de1f3c8a42/build-end.log

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libdrm/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_LIBDRM
 	bool "libdrm"
 	select BR2_PACKAGE_LIBPTHREAD_STUBS
+	depends on BR2_TOOLCHAIN_HAS_THREADS # libpthread-stubs
 	depends on BR2_LARGEFILE
 	help
 	  Direct Rendering Manager
@@ -59,5 +60,5 @@ endmenu
 
 endif
 
-comment "libdrm needs a toolchain w/ largefile"
-	depends on !BR2_LARGEFILE
+comment "libdrm needs a toolchain w/ largefile, threads"
+	depends on !BR2_LARGEFILE || !BR2_TOOLCHAIN_HAS_THREADS