Move java.sdkSpec to the android package

... in preparation for making the handling of sdk versions consistent
across java and cc modules.

Bug: 175678607
Test: m
Change-Id: I598f0454bce9b7320621022115412fbe97403945
diff --git a/android/Android.bp b/android/Android.bp
index 773aa6a..a32e8f2 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -67,6 +67,7 @@
         "rule_builder.go",
         "sandbox.go",
         "sdk.go",
+        "sdk_version.go",
         "singleton.go",
         "singleton_module.go",
         "soong_config_modules.go",