Add cc_library.target.vendor.no_stubs

This is to handle libz special case. libz has stubs but not an LLNDK.
So, libz.vendor should be treated as non-stub-providing libraries and
Vendor APEX should bundle it if it's used by its contents.

libz will set no_stubs for vendor/product variants.

Bug: 313806237
Test: go tests ./apex/...
Change-Id: I10759d7073838909126f8bfe87654f11aa02fd32

cc/library.go

@@ -107,6 +107,13 @@ type LibraryProperties struct {
 			Suffix *string `android:"arch_variant"`
 
 			Header_abi_checker headerAbiCheckerProperties
+
+			// Disable stubs for vendor/product variants
+			// This is a workaround to keep `stubs` only for "core" variant (not product/vendor).
+			// It would be nice if we could put `stubs` into a `target: { core: {} }`
+			// block but it's not supported in soong yet. This could be removed/simplified once we have
+			// a better syntax.
+			No_stubs bool
 		}
 
 		Platform struct {