[llvm-cov] Disable zlib compression in a test input, unbreaks bots

Disable name compression in the inputs used to produce
multiple-files.covmapping. Should fix bots which don't compile with
zlib:

  http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/19610/steps/test/logs/stdio

llvm-svn: 280898