Migrate java/androidmk.go to new system #1

This change migrates some of AndroidMk()s in java/androidmk.go to
AndroidMkEntries(), mainly focusing on deduping test-related helper
funcs.

Test: Soong tests
Test: Built a system image
Test: Manual inspection of diffs
Change-Id: I7810085521600d9ea2df078837688ade41c04825
diff --git a/android/androidmk.go b/android/androidmk.go
index 124523f..589f046 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -80,12 +80,14 @@
 	footer bytes.Buffer
 
 	ExtraEntries []AndroidMkExtraEntriesFunc
+	ExtraFooters []AndroidMkExtraFootersFunc
 
 	EntryMap   map[string][]string
 	entryOrder []string
 }
 
 type AndroidMkExtraEntriesFunc func(entries *AndroidMkEntries)
+type AndroidMkExtraFootersFunc func(w io.Writer, name, prefix, moduleDir string, entries *AndroidMkEntries)
 
 func (a *AndroidMkEntries) SetString(name, value string) {
 	if _, ok := a.EntryMap[name]; !ok {
@@ -254,9 +256,21 @@
 
 	// Write to footer.
 	fmt.Fprintln(&a.footer, "include "+a.Include)
+	blueprintDir := filepath.Dir(bpPath)
+	for _, footerFunc := range a.ExtraFooters {
+		footerFunc(&a.footer, name, prefix, blueprintDir, a)
+	}
 }
 
 func (a *AndroidMkEntries) write(w io.Writer) {
+	if a.Disabled {
+		return
+	}
+
+	if !a.OutputFile.Valid() {
+		return
+	}
+
 	w.Write(a.header.Bytes())
 	for _, name := range a.entryOrder {
 		fmt.Fprintln(w, name+" := "+strings.Join(a.EntryMap[name], " "))
@@ -264,6 +278,10 @@
 	w.Write(a.footer.Bytes())
 }
 
+func (a *AndroidMkEntries) FooterLinesForTests() []string {
+	return strings.Split(string(a.footer.Bytes()), "\n")
+}
+
 func AndroidMkSingleton() Singleton {
 	return &androidMkSingleton{}
 }