Fix dangling rules on aosp_cf_x86_phone

aosp_cf_x86_phone uses SecondArchIsTranslated, which was leaving
a dangling rule from the oatdump rules to
out/soong/vsoc_x86/dex_bootjars/system/framework/arm/boot.art.
Consolidate the code to select targets for dexpreopting and use it
in more places to prevent references to boot images that were not
generated.

Test: m checkbuild
Change-Id: Ia4945a99ff5e575e759299106559c85f38489acc