cmTarget: Allow transitive evaluation of SOURCES property.

Extend the cmGeneratorExpressionDAGChecker with an interface
returning the name of the top target.  Use that to determine
when there is a DAG violation, as required by the RunCMake.Languages
tests.

1 files changed, 7 insertions, 0 deletions

diff --git a/Tests/ConfigSources/iface_debug_src.cpp b/Tests/ConfigSources/iface_debug_src.cpp
new file mode 100644
index 0000000..63b22fc
--- /dev/null
+++ b/Tests/ConfigSources/iface_debug_src.cpp
@@ -0,0 +1,7 @@
+
+#include "iface_debug.h"
+
+int iface_debug()
+{
+  return 0;
+}