Install recovery etc files to recovery/root/system/etc.

They used to be installed under recovery/root/etc. This CL moves the
files to the new location and creates a symlink from /etc to /system/etc
(done by the rule in system/core/rootdir). This gives similar layout
between normal boot and recovery, and allows installing prebuilt_etc
files with Soong (`recovery_available: true`).

As part of the change, we no longer need the whitelisting rule for
mke2fs.conf.

Bug: 112780007
Test: Build with other changes in the topic (aosp_taimen-userdebug).
      Check the generated files under recovery (/etc being a symlink to
      /system/etc).
Test: Boot into recovery. Verify basic functionalities (`adb shell` and
      `adb sideload`, factory reset).
Test: `build/soong/build_test.bash --dist`
Change-Id: Ibb6dea6f179a339f0c2d0fd8ba05ec0085b79a12
diff --git a/core/Makefile b/core/Makefile
index 6c5636c..8b74f9b 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -1117,8 +1117,10 @@
 	$(hide) mkdir -p $(dir $@)
 	$(hide) openssl x509 -pubkey -noout -in $< > $@
 
-ALL_DEFAULT_INSTALLED_MODULES += $(TARGET_RECOVERY_ROOT_OUT)/etc/update_engine/update-payload-key.pub.pem
-$(TARGET_RECOVERY_ROOT_OUT)/etc/update_engine/update-payload-key.pub.pem: $(TARGET_OUT_ETC)/update_engine/update-payload-key.pub.pem
+ALL_DEFAULT_INSTALLED_MODULES += \
+    $(TARGET_RECOVERY_ROOT_OUT)/system/etc/update_engine/update-payload-key.pub.pem
+$(TARGET_RECOVERY_ROOT_OUT)/system/etc/update_engine/update-payload-key.pub.pem: \
+		$(TARGET_OUT_ETC)/update_engine/update-payload-key.pub.pem
 	$(hide) cp -f $< $@
 endif
 endif
@@ -1605,10 +1607,10 @@
 define build-recoveryimage-target
   # Making recovery image
   $(hide) mkdir -p $(TARGET_RECOVERY_OUT)
-  $(hide) mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/etc $(TARGET_RECOVERY_ROOT_OUT)/sdcard $(TARGET_RECOVERY_ROOT_OUT)/tmp
+  $(hide) mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/sdcard $(TARGET_RECOVERY_ROOT_OUT)/tmp
   # Copying baseline ramdisk...
   # Use rsync because "cp -Rf" fails to overwrite broken symlinks on Mac.
-  $(hide) rsync -a --exclude=etc --exclude=sdcard $(IGNORE_RECOVERY_SEPOLICY) $(IGNORE_CACHE_LINK) $(TARGET_ROOT_OUT) $(TARGET_RECOVERY_OUT)
+  $(hide) rsync -a --exclude=sdcard $(IGNORE_RECOVERY_SEPOLICY) $(IGNORE_CACHE_LINK) $(TARGET_ROOT_OUT) $(TARGET_RECOVERY_OUT)
   # Modifying ramdisk contents...
   $(if $(BOARD_RECOVERY_KERNEL_MODULES), \
     $(call build-image-kernel-modules,$(BOARD_RECOVERY_KERNEL_MODULES),$(TARGET_RECOVERY_ROOT_OUT),,$(call intermediates-dir-for,PACKAGING,depmod_recovery)))
@@ -1623,9 +1625,9 @@
   $(hide) $(foreach item,$(TARGET_PRIVATE_RES_DIRS), \
     cp -rf $(item) $(TARGET_RECOVERY_ROOT_OUT)/$(newline))
   $(hide) $(foreach item,$(recovery_fstab), \
-    cp -f $(item) $(TARGET_RECOVERY_ROOT_OUT)/etc/recovery.fstab)
+    cp -f $(item) $(TARGET_RECOVERY_ROOT_OUT)/system/etc/recovery.fstab)
   $(if $(strip $(recovery_wipe)), \
-    $(hide) cp -f $(recovery_wipe) $(TARGET_RECOVERY_ROOT_OUT)/etc/recovery.wipe)
+    $(hide) cp -f $(recovery_wipe) $(TARGET_RECOVERY_ROOT_OUT)/system/etc/recovery.wipe)
   $(hide) cp $(RECOVERY_INSTALL_OTA_KEYS) $(TARGET_RECOVERY_ROOT_OUT)/res/keys
   $(hide) ln -sf prop.default $(TARGET_RECOVERY_ROOT_OUT)/default.prop
   $(BOARD_RECOVERY_IMAGE_PREPARE)