Fix diffs in system_other image

Make seems to use functionality of build_image that relies on the
output filename. So it sees that the output is system_other.img and
makes changes based on that. We don't use that codepath, so make those
changes ourselves.

Bug: 376539388
Test: diff out/target/product/vsoc_x86_64/system_other.img out/soong/.intermediates/build/soong/fsgen/aosp_cf_x86_64_phone_generated_system_other_image/android_common/system_other.img
Change-Id: I425b54efc5412e780369b2a851606bd1f1c99ae3