Check consistency of the BootJars/UpdatableBootJars config

Both out/soong/dexpreopt.config and out/soong/soong.variables contain
configuration for the BootJars and UpdatableBootJars that MUST be
identical. If they are not then it can lead to broken builds.

This change adds a consistency check for them that will make the issue
more obvious.

Bug: 186195980
Test: DIST_DIR=out/bionic-dist ./art/tools/dist_linux_bionic.sh -j80 com.android.art.host com.android.support.apexer --skip-soong-tests
      Ran the previous command with and without the fix in
      https://r.android.com/1684877. Without the fix the build reported
      an inconsistency in the configuration, with that fix the build
      passed.
Change-Id: I10fbe328ba4f1fbd9db4708409979e9824c196ef