Export makevars ANDROID_JAVA{8,9}_HOME.

These variables are published by config.go for use inside
.mk scripts. They are suitable for rules that need to be
pinned to a particular java/javac version because they do
not (yet) support the other.

Bug: 70286093
Test: Treehugger
Change-Id: Id407fca187fdf6c1947fc9d1ed7cd634fe089384
Merged-In: Id407fca187fdf6c1947fc9d1ed7cd634fe089384

java/config/makevars.go

@@ -36,6 +36,8 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 	}
 
 	ctx.Strict("ANDROID_JAVA_HOME", "${JavaHome}")
+	ctx.Strict("ANDROID_JAVA8_HOME", "prebuilts/jdk/jdk8/${hostPrebuiltTag}")
+	ctx.Strict("ANDROID_JAVA9_HOME", "prebuilts/jdk/jdk9/${hostPrebuiltTag}")
 	ctx.Strict("ANDROID_JAVA_TOOLCHAIN", "${JavaToolchain}")
 	ctx.Strict("JAVA", "${JavaCmd}")
 	ctx.Strict("JAVAC", "${JavacCmd}")