LINK_LIBRARIES: Add support for LINK_ONLY genex

Previously we always used content guarded by `$<LINK_ONLY:...>`
in `LINK_LIBRARIES`, even when evaluating for non-linking usage
requirements.  Add a policy to honor `LINK_ONLY` in `LINK_LIBRARIES`
the same way we already do in `INTERFACE_LINK_LIBRARIES`.

1 files changed, 8 insertions, 0 deletions

diff --git a/Tests/InterfaceLinkLibraries/foo_link_only.c b/Tests/InterfaceLinkLibraries/foo_link_only.c
new file mode 100644
index 0000000..9ca1c01
--- /dev/null
+++ b/Tests/InterfaceLinkLibraries/foo_link_only.c
@@ -0,0 +1,8 @@
+#ifndef FOO_LINK_ONLY
+#  error "FOO_LINK_ONLY incorrectly not defined"
+#endif
+
+int foo_link_only(void)
+{
+  return 0;
+}