Fix cmake po detection bug

Previously, cmake po detection would treat the "timestamp" file created by building for android as own language directory.

cmake/Modules/FindGettextLib.cmake

@@ -74,6 +74,7 @@ IF(GETTEXT_FOUND)
 	SET(GETTEXT_MO_DEST_PATH ${LOCALEDIR}/<locale>/LC_MESSAGES)
 	FILE(GLOB GETTEXT_AVAILABLE_LOCALES RELATIVE ${GETTEXT_PO_PATH} "${GETTEXT_PO_PATH}/*")
 	LIST(REMOVE_ITEM GETTEXT_AVAILABLE_LOCALES minetest.pot)
+	LIST(REMOVE_ITEM GETTEXT_AVAILABLE_LOCALES timestamp)
 	MACRO(SET_MO_PATHS _buildvar _destvar _locale)
 		STRING(REPLACE "<locale>" ${_locale} ${_buildvar} ${GETTEXT_MO_BUILD_PATH})
 		STRING(REPLACE "<locale>" ${_locale} ${_destvar} ${GETTEXT_MO_DEST_PATH})