Verify that Android targets generate DWARF 4 by default.

Summary:
In the future, Android releases will support DWARF 5, but we need to
ensure that older targets only have DWARF 4 generated for them. This
patch inserts that verification for all Android releases now. The patch
also fixes 2 minor mistakes (a mistakenly moved RUN line, and the
missing G_DWARF2 check label).

Reviewers: aprantl

Reviewed By: aprantl

Subscribers: chh, pirama, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60238

llvm-svn: 357713