fs_config_generate_$(TARGET_DEVICE) is built based off the content
of $(TARGET_ANDROID_FILESYSTEM_CONFIG_H). We also add the rules
fs_config_dirs and fs_config_file to utilize this command
for target contents:
fs_config_generate_$(TARGET_DEVICE) -D -o system/etc/fs_config_dir
fs_config_generate_$(TARGET_DEVICE) -F -o system/etc/fs_config_file
In order to use this feature, one must have the fs_config_dirs and
fs_config_files in the $(PRODUCT_PACKAGES) list defined in the
device make files in $(TARGET_DEVICE_DIR). And either an
android_filesystem_config.h file in that directory, or define a
path in TARGET_ANDROID_FILESYSTEM_CONFIG_H to point to one.
Bug: 19908228
Change-Id: Iee1543d99169f874e0915ae07962a7750ecb6342
