Add libxpm as a dependency of ace_of_penguins

ace_of_penguins fails to build when xlib_libXpm is not selected. Add
it has a dependency. However, contrary to normal dependencies to
libraries (where we use 'select') we use 'depends on' here, otherwise
the X.org server will be get selected automatically without the user
noticing.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/games/ace_of_penguins/Config.in

@@ -2,6 +2,7 @@ config BR2_PACKAGE_ACE_OF_PENGUINS
 	bool "ace_of_penguins"
 	select BR2_PACKAGE_LIBPNG
 	depends on BR2_PACKAGE_XORG7
+	depends on BR2_PACKAGE_XLIB_LIBXPM
 	help
 	  The Ace of Penguins is a set of Unix/X solitaire games based
 	  on the ones available for Windows but with a number of

package/games/ace_of_penguins/ace_of_penguins.mk

@@ -10,6 +10,6 @@ ACE_OF_PENGUINS_AUTORECONF = YES
 ACE_OF_PENGUINS_STAGING = NO
 ACE_OF_PENGUINS_TARGET = YES
 
-ACE_OF_PENGUINS_DEPENDENCIES = libpng xserver_xorg-server
+ACE_OF_PENGUINS_DEPENDENCIES = libpng xserver_xorg-server xlib_libXpm
 
 $(eval $(call AUTOTARGETS,package/games,ace_of_penguins))