Fix explicitly versioned tag

The explicitlyVersion flag was being set on a local copy of the
tag, not the one that was being used later to add the dependenc.

Test: TestApexVerifyNativeImplementationLibs
Flag: EXEMPT bugfix
Change-Id: I7339267659f74bee088dfe345f7cc56319306b53
diff --git a/cc/cc.go b/cc/cc.go
index 4b2b417..6658c05 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -2349,6 +2349,10 @@
 		variations = append(variations, blueprint.Variation{Mutator: "version", Variation: version})
 		if tag, ok := depTag.(libraryDependencyTag); ok {
 			tag.explicitlyVersioned = true
+			// depTag is an interface that contains a concrete non-pointer struct.  That makes the local
+			// tag variable a copy of the contents of depTag, and updating it doesn't change depTag.  Reassign
+			// the modified copy to depTag.
+			depTag = tag
 		} else {
 			panic(fmt.Errorf("Unexpected dependency tag: %T", depTag))
 		}