Add NDK API codenames for old releases.

Without these, we'd need to go rewrite all the stub templates to stop
using the codename and use the number instead whenever an API is
released.

Test: changed something in libc to use introduced=L, make ndk
Bug: None
Change-Id: I1b8703655664c567f8a5c36219e73f11ba27d99a

android/api_levels.go

@@ -55,7 +55,19 @@ func GetApiLevelsJson(ctx PathContext) Path {
 
 func (a *apiLevelsSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
 	baseApiLevel := 9000
-	apiLevelsMap := map[string]int{}
+	apiLevelsMap := map[string]int{
+		"G":     9,
+		"I":     14,
+		"J":     16,
+		"J-MR1": 17,
+		"J-MR2": 18,
+		"K":     19,
+		"L":     21,
+		"L-MR1": 22,
+		"M":     23,
+		"N":     24,
+		"N-MR1": 25,
+	}
 	for i, codename := range ctx.Config().(Config).PlatformVersionAllCodenames() {
 		apiLevelsMap[codename] = baseApiLevel + i
 	}