Reland: Moving GSI-specific files to system_ext

Only common files can reside in system partition, other files
should be moved to the newly added system_ext partition.

Note that for GSI, it will be a single system.img that includes the
contents of product and system_ext partitions, under /system/product
and /system/system_ext, respectively. After moving skip_mount.cfg to
system_ext partition, it also needs a symlink file under system
partition:

  /system/etc/init/config -> /system/system_ext/etc/init/config

This allows Q-launched first-stage init (in /boot partition) continue
to use the same path when new GSI image is used.

Bug: 138281441
Test: build aosp_arm64-userdebug and boot it on crosshatch
Test: rm -rf out && build/soong/soong_ui.bash --make-mode \
      TARGET_PRODUCT=aosp_arm64 TARGET_BUILD_VARIANT=userdebug droid
Change-Id: Iae9f5fb688f49497563864eb882d5f0ae33c744a

CleanSpec.mk

@@ -655,6 +655,10 @@ $(call add-clean-step, rm -rf $(OUT_DIR)/target/product/generic*/*system_ext*)
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/product/generic*/*/product)
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/product/generic*/*/system_ext)
 
+# Move GSI-specific files from /system to /system/system_ext
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/etc/init/init.gsi.rc)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/etc/init/config/)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************

target/product/gsi/Android.mk

@@ -169,3 +169,38 @@ _binder32 :=
 include $(BUILD_PHONY_PACKAGE)
 
 endif # BOARD_VNDK_VERSION is set
+
+#####################################################################
+# skip_mount.cfg, read by init to skip mounting some partitions when GSI is used.
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := gsi_skip_mount.cfg
+LOCAL_MODULE_STEM := skip_mount.cfg
+LOCAL_SRC_FILES := $(LOCAL_MODULE)
+LOCAL_MODULE_CLASS := ETC
+LOCAL_SYSTEM_EXT_MODULE := true
+LOCAL_MODULE_RELATIVE_PATH := init/config
+
+# Adds a symlink under /system/etc/init/config pointing to /system/system_ext/etc/init/config
+# because first-stage init in Android 10.0 will read the skip_mount.cfg from /system/etc/* after
+# chroot /system.
+# TODO: remove this symlink when no need to support new GSI on Android 10.
+# The actual file needs to be under /system/system_ext because it's GSI-specific and does not
+# belong to core CSI.
+LOCAL_POST_INSTALL_CMD := \
+    mkdir -p $(TARGET_OUT)/etc/init; \
+    ln -sf /system/system_ext/etc/init/config $(TARGET_OUT)/etc/init/config
+
+include $(BUILD_PREBUILT)
+
+#####################################################################
+# init.gsi.rc, GSI-specific init script.
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := init.gsi.rc
+LOCAL_SRC_FILES := $(LOCAL_MODULE)
+LOCAL_MODULE_CLASS := ETC
+LOCAL_SYSTEM_EXT_MODULE := true
+LOCAL_MODULE_RELATIVE_PATH := init
+
+include $(BUILD_PREBUILT)

target/product/gsi_common.mk

@@ -50,11 +50,6 @@ PRODUCT_ARTIFACT_PATH_REQUIREMENT_WHITELIST += \
 # Some GSI builds enable dexpreopt, whitelist these preopt files
 PRODUCT_ARTIFACT_PATH_REQUIREMENT_WHITELIST += %.odex %.vdex %.art
 
-# Exclude GSI specific files
-PRODUCT_ARTIFACT_PATH_REQUIREMENT_WHITELIST += \
-    system/etc/init/config/skip_mount.cfg \
-    system/etc/init/init.gsi.rc \
-
 # Exclude all files under system/product and system/system_ext
 PRODUCT_ARTIFACT_PATH_REQUIREMENT_WHITELIST += \
     system/product/% \
@@ -71,9 +66,9 @@ PRODUCT_USE_DYNAMIC_PARTITION_SIZE := true
 PRODUCT_COMPATIBLE_PROPERTY_OVERRIDE := true
 
 # GSI specific tasks on boot
-PRODUCT_COPY_FILES += \
-    build/make/target/product/gsi/skip_mount.cfg:system/etc/init/config/skip_mount.cfg \
-    build/make/target/product/gsi/init.gsi.rc:system/etc/init/init.gsi.rc \
+PRODUCT_PACKAGES += \
+    gsi_skip_mount.cfg \
+    init.gsi.rc
 
 # Support addtional P vendor interface
 PRODUCT_EXTRA_VNDK_VERSIONS := 28

target/product/gsi_release.mk

@@ -24,11 +24,6 @@
 # - etc.
 #
 
-# Exclude GSI specific files
-PRODUCT_ARTIFACT_PATH_REQUIREMENT_WHITELIST += \
-    system/etc/init/config/skip_mount.cfg \
-    system/etc/init/init.gsi.rc \
-
 # Exclude all files under system/product and system/system_ext
 PRODUCT_ARTIFACT_PATH_REQUIREMENT_WHITELIST += \
     system/product/% \
@@ -50,9 +45,9 @@ PRODUCT_USE_DYNAMIC_PARTITION_SIZE := true
 PRODUCT_COMPATIBLE_PROPERTY_OVERRIDE := true
 
 # GSI specific tasks on boot
-PRODUCT_COPY_FILES += \
-    build/make/target/product/gsi/skip_mount.cfg:system/etc/init/config/skip_mount.cfg \
-    build/make/target/product/gsi/init.gsi.rc:system/etc/init/init.gsi.rc \
+PRODUCT_PACKAGES += \
+    gsi_skip_mount.cfg \
+    init.gsi.rc
 
 # Support addtional P VNDK packages
 PRODUCT_EXTRA_VNDK_VERSIONS := 28