libunwind: needs set/getcontext, which only got added to uClibc post-0.9.33

Fixes http://autobuild.buildroot.net/results/3e8/3e8670ab1454118baf1e4a5ca632d45963ba3781/

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libunwind/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_LIBUNWIND
 	bool "libunwind"
 	depends on BR2_TOOLCHAIN_HAS_THREADS
+	depends on (BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC) # {g,s}etcontext
 	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
 		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
 	help
@@ -8,7 +9,8 @@ config BR2_PACKAGE_LIBUNWIND
 
 	  http://www.nongnu.org/libunwind/index.html
 
-comment "libunwind needs a toolchain w/ threads"
+comment "libunwind needs a uclibc snapshot or (e)glibc toolchain w/ threads"
 	depends on BR2_arm || BR2_armeb || BR2_mips || BR2_mipsel || BR2_mips64 || \
 		BR2_mips64el || BR2_powerpc || BR2_sh || BR2_sh64 || BR2_i386 || BR2_x86_64
 	depends on !BR2_TOOLCHAIN_HAS_THREADS
+	depends on !(BR2_UCLIBC_VERSION_SNAPSHOT || BR2_TOOLCHAIN_USES_GLIBC)