Genex: Fix stack overflow in transitive property evaluation.

Commit v2.8.11~156^2~2 (Expand includes and defines transitively
in 'external' genexes., 2013-02-13) introduced a recursive loop
and a stack overflow during evaluation of a link implementation
which depends on a transitive property, such as

 add_library(empty1 ...)
 add_library(empty2 ...)
 target_link_libraries(empty1
   PRIVATE
     $<$<STREQUAL:$<TARGET_PROPERTY:INCLUDE_DIRECTORIES>,/foo/bar>:empty2>
 )

There is no use-case for code like that currently, but it should not
cause a stack overflow.

Avoid the recursion by reporting an error early if a case like this
is found.

1 files changed, 14 insertions, 0 deletions

diff --git a/Tests/RunCMake/TargetPropertyGeneratorExpressions/LinkImplementationCycle4.cmake b/Tests/RunCMake/TargetPropertyGeneratorExpressions/LinkImplementationCycle4.cmake
new file mode 100644
index 0000000..ab6d0b2
--- /dev/null
+++ b/Tests/RunCMake/TargetPropertyGeneratorExpressions/LinkImplementationCycle4.cmake
@@ -0,0 +1,14 @@
+
+add_library(empty1 empty.cpp)
+add_library(empty2 empty.cpp)
+
+# The INTERFACE_INCLUDE_DIRECTORIES do not depend on the link interface.
+# On its own, this is fine. It is only when used by empty3 that an error
+# is appropriately issued.
+target_link_libraries(empty1
+  INTERFACE
+    $<$<STREQUAL:$<TARGET_PROPERTY:INTERFACE_INCLUDE_DIRECTORIES>,/foo/bar>:empty2>
+)
+
+add_library(empty3 empty.cpp)
+target_link_libraries(empty3 empty1)