package/efl: add libunwind optional dependency

There is no configure option to enable/disable libunwind support.
See efl/m4/efl_libunwind.m4

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

package/efl/efl.mk

@@ -293,6 +293,10 @@ endef
 EFL_POST_INSTALL_TARGET_HOOKS = EFL_HOOK_REMOVE_UPOWER
 endif
 
+ifeq ($(BR2_PACKAGE_LIBUNWIND),y)
+EFL_DEPENDENCIES += libunwind
+endif
+
 $(eval $(autotools-package))
 
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