Optimize: Reduce vendor target build files

Prevent system/% files from being built by BUILDING_SYSTEM_IMAGE
and data/% files from being built by BUILDING_USERDATA_IMAGE

1) Address issue where system/% files were
being built even when
PRODUCT_BUILD_SYSTEM_IMAGE was false.
 This change reduces the ninja targets for
aosp_cf_x86_64_phone_vendor-trunk_staging-userdebug
from 140,427 to 57,303

Test:
lunch aosp_cf_x86_64_phone_vendor-trunk_staging-userdebug ; m

2) Resolve issue where data/% files were
being built during "m dist" even if
PRODUCT_BUILD_USERDATA_IMAGE was set to false

Test: Set any module to install at data partition using
LOCAL_MODULE_PATH=$(TARGET_OUT_DATA)/app
lunch aosp_cf_x86_64_phone_vendor-trunk_staging-userdebug ; m dist
Check the contents at out/target/product/vsoc_x86_64 and out/dist

Change-Id: I2a914339231d57598a6f30fc83fd8203d4107a11