Rebuild buildinfo.prop after installclean

aosp/1317598 has made a regression that the dependency from
buildinfo.prop to INSTALLED_ANDROID_INFO_TXT_TARGET is removed. As a
result, buildinfo.prop is not re-builty even after installclean, which
caused inconsistency between  ro.build.display.id (from buildinfo.prop)
and ro.system.build.fingerprint (from build.prop which is re-built).

Fixing the issue by moving buildinfo.prop from $(call
intermediates-dir-for,ETC) to $(call intermediates-dir-for,PACKAGING)
so that it gets deleted by installclean.

Bug: 158583916
Test: m out/target/product/generic_arm64/system/build.prop
m installclean
m out/target/product/generic_arm64/system/build.prop
Inspect out/soong/verbose.gz and check that buildinfo.prop was newly
created.

Change-Id: Id82b8fdc872deffb6a1764ca6d3c7114301dee1d