cmTarget: Fix system include annotation propagation.

Direct users of IMPORTED targets treat INTERFACE_INCLUDE_DIRECTORIES
as SYSTEM, after commit a63fcbcb (Always consider includes from IMPORTED
targets to be SYSTEM., 2013-08-29).  It was intended that transitive
use of an IMPORTED target would have the same behavior, but that
did not work.  The implementation processed only direct dependencies
in cmTarget::FinalizeSystemIncludeDirectories.

Implement transitive evaluation of dependencies by traversing the
link interface of each target in the link implementation.

1 files changed, 4 insertions, 0 deletions

diff --git a/Tests/IncludeDirectories/SystemIncludeDirectories/CMakeLists.txt b/Tests/IncludeDirectories/SystemIncludeDirectories/CMakeLists.txt
index 1f5c93b..abe9f74 100644
--- a/Tests/IncludeDirectories/SystemIncludeDirectories/CMakeLists.txt
+++ b/Tests/IncludeDirectories/SystemIncludeDirectories/CMakeLists.txt
@@ -25,6 +25,10 @@ add_library(imported_consumer imported_consumer.cpp)
 target_link_libraries(imported_consumer iface)
 target_compile_options(imported_consumer PRIVATE -Werror=unused-variable)
 
+add_library(imported_consumer2 imported_consumer.cpp)
+target_link_libraries(imported_consumer2 imported_consumer)
+target_compile_options(imported_consumer2 PRIVATE -Werror=unused-variable)
+
 macro(do_try_compile error_option)
   set(TC_ARGS
     IFACE_TRY_COMPILE_${error_option}