Package llvm-cov in llvm-profdata.zip (take 2)

Bug: http://b/214396112

It is needed for code coverage smoke test.  Retain the
`llvm-profdata.zip` name since it is used in Tradefed.

This fixes aosp/2017370 which incorrectly packaged llvm-profdata twice.

Test: `CLANG_COVERAGE=true m dist` and inspect llvm-profdata.zip
Change-Id: Ic1cbebff3f6fbea04a6c58c6d57557d0ffde14ae