Support LOCAL_PACKAGE_SPLITS.

Support LOCAL_PACKAGE_SPLITS, which accepts a list of resource lables
and generates multiple apks. The build system sets up rules to sign and
zipalign the split apks.

Bug: 16319961
Change-Id: I344b3d1c7eb158c6d0df879093d666a89870aadd

core/base_rules.mk

@@ -176,7 +176,6 @@ else
   built_module_path := $(intermediates)
 endif
 LOCAL_BUILT_MODULE := $(built_module_path)/$(my_built_module_stem)
-built_module_path :=
 
 ifneq (true,$(LOCAL_UNINSTALLABLE_MODULE))
   # Apk and its attachments reside in its own subdir.

core/clear_vars.mk

@@ -23,6 +23,7 @@ LOCAL_PACKAGE_NAME:=
 LOCAL_OVERRIDES_PACKAGES:=
 LOCAL_EXPORT_PACKAGE_RESOURCES:=
 LOCAL_MANIFEST_PACKAGE_NAME:=
+LOCAL_PACKAGE_SPLITS:=
 LOCAL_REQUIRED_MODULES:=
 LOCAL_ACP_UNAVAILABLE:=
 LOCAL_MODULE_TAGS:=

core/definitions.mk

@@ -1805,6 +1805,18 @@ $(hide) $(ZIPALIGN) -f 4 $@.unaligned $@.aligned
 $(hide) mv $@.aligned $@
 endef
 
+# Build a split APK
+# The splti APKs are already built in the same command building the base APK.
+# We only need to do zipalign and signing etc.
+# This macro must be called with $(eval).
+# $(1): the path to the built split APK.
+# $(2): the path to the base APK.
+define build-split-apk
+$(1) : $(2)
+	$$(sign-package)
+	$$(align-package)
+endef
+
 define install-dex-debug
 $(hide) if [ -f "$(PRIVATE_INTERMEDIATES_DIR)/classes.dex" ]; then \
 	    mkdir -p $(TOP)/dalvik/DEBUG-FILES; \

core/package_internal.mk

@@ -68,6 +68,10 @@ ifeq ($(filter tests, $(LOCAL_MODULE_TAGS)),)
 LOCAL_AAPT_FLAGS := $(LOCAL_AAPT_FLAGS) -z
 endif
 
+ifdef LOCAL_PACKAGE_SPLITS
+LOCAL_AAPT_FLAGS += $(addprefix --split ,$(LOCAL_PACKAGE_SPLITS))
+endif
+
 ifeq (,$(LOCAL_ASSET_DIR))
 LOCAL_ASSET_DIR := $(LOCAL_PATH)/assets
 endif
@@ -403,6 +407,32 @@ $(built_odex) : $(built_dex)
 	$(hide) rm $@.input
 endif
 
+###############################
+## APK splits
+ifdef LOCAL_PACKAGE_SPLITS
+built_apk_splits := $(foreach s,$(LOCAL_PACKAGE_SPLITS),$(built_module_path)/package_$(s).apk)
+installed_apk_splits := $(foreach s,$(LOCAL_PACKAGE_SPLITS),$(my_module_path)/$(LOCAL_MODULE)_$(s).apk)
+
+$(built_apk_splits): PRIVATE_PRIVATE_KEY := $(private_key)
+$(built_apk_splits): PRIVATE_CERTIFICATE := $(certificate)
+# The splits should have been built in the same command building the base apk.
+# This rule just establishes the dependency and make sure the splits are up to date.
+$(foreach s,$(built_apk_splits),\
+  $(eval $(call build-split-apk,$(s),$(LOCAL_BUILT_MODULE))))
+
+# Rules to install the splits
+$(foreach s,$(LOCAL_PACKAGE_SPLITS),\
+  $(eval $(call copy-one-file,$(built_module_path)/package_$(s).apk,$(my_module_path)/$(LOCAL_MODULE)_$(s).apk)))
+
+# Register the additional built and installed files.
+ALL_MODULES.$(my_register_name).INSTALLED += $(installed_apk_splits)
+ALL_MODULES.$(my_register_name).BUILT_INSTALLED += \
+  $(foreach s,$(LOCAL_PACKAGE_SPLITS),$(built_module_path)/package_$(s).apk:$(my_module_path)/$(LOCAL_MODULE)_$(s).apk)
+
+# Make sure to install the splits when you run "make <module_name>".
+$(my_register_name): $(installed_apk_splits)
+endif # LOCAL_PACKAGE_SPLITS
+
 # Save information about this package
 PACKAGES.$(LOCAL_PACKAGE_NAME).OVERRIDES := $(strip $(LOCAL_OVERRIDES_PACKAGES))
 PACKAGES.$(LOCAL_PACKAGE_NAME).RESOURCE_FILES := $(all_resources)