package/xenomai: introduce a BR2_PACKAGE_XENOMAI_ARCH_SUPPORTS option

Introduce BR2_PACKAGE_XENOMAI_ARCH_SUPPORTS to hold the
architectures than can build and use Xenomai on the target.

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

package/xenomai/Config.in

@@ -1,13 +1,17 @@
-comment "xenomai needs a toolchain w/ threads"
-	depends on !BR2_TOOLCHAIN_HAS_THREADS
+config BR2_PACKAGE_XENOMAI_ARCH_SUPPORTS
+	bool
+	default y
 	depends on BR2_i386 || BR2_x86_64 || BR2_arm || \
 		   BR2_bfin || BR2_powerpc || BR2_sh4
 
+comment "xenomai needs a toolchain w/ threads"
+	depends on !BR2_TOOLCHAIN_HAS_THREADS
+	depends on BR2_PACKAGE_XENOMAI_ARCH_SUPPORTS
+
 config BR2_PACKAGE_XENOMAI
 	bool "Xenomai Userspace"
+	depends on BR2_PACKAGE_XENOMAI_ARCH_SUPPORTS
 	depends on BR2_TOOLCHAIN_HAS_THREADS
-	depends on BR2_i386 || BR2_x86_64 || BR2_arm || \
-		BR2_bfin || BR2_powerpc || BR2_sh4
 	help
 	  Real-Time Framework for Linux
 	  http://www.xenomai.org