Pass FRAMEWORK_VBMETA_VERSION to assemble_vintf

Note that this depends on a change in avbtool:
  https://android-review.googlesource.com/#/c/406374/

Bug: 38325029
Test: builds system.img, checks $OUT/system/compatibility_matrix.xml
      contains correct vbmeta-version
Change-Id: Iacc0a2687fb39600ad6b8e9cfbfe5c1a3b90b40b