Support build old version of cts

Bug: 27508747
Change-Id: I3d474f6f6534e172ecf1d0a6c833a9dfa6164344
diff --git a/core/ninja.mk b/core/ninja.mk
index 2878514..d2e882d 100644
--- a/core/ninja.mk
+++ b/core/ninja.mk
@@ -43,6 +43,7 @@
 	eng \
 	fusion \
 	oem_image \
+	old-cts \
 	online-system-api-sdk-docs \
 	pdk \
 	platform \