Honor $<LINK_ONLY> when checking interface properties

Callers of cmTarget::GetLinkImplementationClosure are interested in the
set of targets whose interface properties propagate to the current
target.  This excludes targets guarded by $<LINK_ONLY>.

Teach the CompatibleInterface test to cover suppression of interface
compatibility tests with $<LINK_ONLY>.  Although this is not recommended
in practice, it is a way of covering the above behavior.

1 files changed, 4 insertions, 0 deletions

diff --git a/Tests/CompatibleInterface/foo.cpp b/Tests/CompatibleInterface/foo.cpp
new file mode 100644
index 0000000..e05eb7e
--- /dev/null
+++ b/Tests/CompatibleInterface/foo.cpp
@@ -0,0 +1,4 @@
+int foo()
+{
+  return 0;
+}