CMake: Emulate interface library on import (#108)

Closes: #104
Signed-off-by: Gregor Jasny <gjasny@googlemail.com>

c-ares-config.cmake.in

@@ -7,10 +7,12 @@ include("${CMAKE_CURRENT_LIST_DIR}/c-ares-targets.cmake")
 set(c-ares_LIBRARY c-ares::cares)
 
 if(@CARES_SHARED@)
-	add_library(c-ares::cares_shared ALIAS c-ares::cares)
+	add_library(c-ares::cares_shared INTERFACE IMPORTED)
+	set_target_properties(c-ares::cares_shared PROPERTIES INTERFACE_LINK_LIBRARIES "c-ares::cares")
 	set(c-ares_SHARED_LIBRARY c-ares::cares_shared)
 elseif(@CARES_STATIC@)
-	add_library(c-ares::cares_static ALIAS c-ares::cares)
+	add_library(c-ares::cares_static INTERFACE IMPORTED)
+	set_target_properties(c-ares::cares_static PROPERTIES INTERFACE_LINK_LIBRARIES "c-ares::cares")
 endif()
 
 if(@CARES_STATIC@)