Add llndk_stubs property

Prepare for making the relationship between an llndk_library stubs
module and the cc_library implementation module explicit by
adding an llndk_stubs property.  Each cc_library will be updated
to point to its llndk_library, and the llndk_library name will
be changed to make the .llndk suffix explicit.  Then the implicit
connection and suffix can be removed.

Bug: 170784825
Test: m checkbuild
Change-Id: I6b0482a3f286ec29b2e928551aa4317749f2b499
diff --git a/apex/apex.go b/apex/apex.go
index a9a58a6..357c3b4 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -2383,11 +2383,12 @@
 							// system libraries.
 							if !am.DirectlyInAnyApex() {
 								// we need a module name for Make
-								name := cc.BaseModuleName() + cc.Properties.SubName
-								if proptools.Bool(a.properties.Use_vendor) {
+								name := cc.ImplementationModuleName(ctx)
+
+								if !proptools.Bool(a.properties.Use_vendor) {
 									// we don't use subName(.vendor) for a "use_vendor: true" apex
 									// which is supposed to be installed in /system
-									name = cc.BaseModuleName()
+									name += cc.Properties.SubName
 								}
 								if !android.InList(name, a.requiredDeps) {
 									a.requiredDeps = append(a.requiredDeps, name)