Don't use APEX stubs between internal libs in the same APEX when

building test_for modules.

This extends the current approach where test modules always depend on
the platform variants of the APEX libs, and only skips the stubs on
them. It still has the limitation that the internal libs must have the
exact same apex_available lists.

Also some improvement of the test accuracy in TestTestFor.

Test: m libartagent-target
  with http://r.android.com/q/topic:libdexfile-noext applied
Bug: 183217299
Change-Id: I2118b8a22c887077867a3ddbbe73437b4a29a6ad

android/apex.go

@@ -453,6 +453,23 @@ func (m *ApexModuleBase) checkApexAvailableProperty(mctx BaseModuleContext) {
 	}
 }
 
+// AvailableToSameApexes returns true if the two modules are apex_available to
+// exactly the same set of APEXes (and platform), i.e. if their apex_available
+// properties have the same elements.
+func AvailableToSameApexes(mod1, mod2 ApexModule) bool {
+	mod1ApexAvail := SortedUniqueStrings(mod1.apexModuleBase().ApexProperties.Apex_available)
+	mod2ApexAvail := SortedUniqueStrings(mod2.apexModuleBase().ApexProperties.Apex_available)
+	if len(mod1ApexAvail) != len(mod2ApexAvail) {
+		return false
+	}
+	for i, v := range mod1ApexAvail {
+		if v != mod2ApexAvail[i] {
+			return false
+		}
+	}
+	return true
+}
+
 type byApexName []ApexInfo
 
 func (a byApexName) Len() int           { return len(a) }