Introduce TARGET_BUILD_UNBUNDLED_IMAGE

- TARGET_BUILD_UNBUNDLED_IMAGE is similar to TARGET_BUILD_APPS, but
its targets are the unbundled partitions instead of apps.
- Rename TARGET_BUILD_APPS_USE_PREBUILT_SDK to TARGET_BUILD_USE_PREBUILT_SDKS
because it is used even without TARGET_BUILD_APPS.
-Instead of TARGET_BUILD_APPS, use TARGET_BUILD_USE_PREBUILT_SDKS
to build java modules with prebuilt sdks, and propagate to Soong.

Bug: 160390776
Test: TARGET_BUILD_UNBUNDLED_IMAGE=true m vendorimage
Change-Id: Ie096212ccbcca0018baae55e106af693b002c9e5
diff --git a/core/java.mk b/core/java.mk
index 2f18ad9..bb4593d 100644
--- a/core/java.mk
+++ b/core/java.mk
@@ -106,8 +106,8 @@
 
 aidl_preprocess_import :=
 ifdef LOCAL_SDK_VERSION
-ifneq ($(filter current system_current test_current core_current, $(LOCAL_SDK_VERSION)$(TARGET_BUILD_APPS_USE_PREBUILT_SDK)),)
-  # LOCAL_SDK_VERSION is current and no TARGET_BUILD_APPS
+ifneq ($(filter current system_current test_current core_current, $(LOCAL_SDK_VERSION)$(TARGET_BUILD_USE_PREBUILT_SDKS)),)
+  # LOCAL_SDK_VERSION is current and no TARGET_BUILD_USE_PREBUILT_SDKS
   aidl_preprocess_import := $(FRAMEWORK_AIDL)
 else
   aidl_preprocess_import := $(call resolve-prebuilt-sdk-aidl-path,$(LOCAL_SDK_VERSION))