Add logs to chrome_elf_unittests to ensure the correct target is built.

If users just build chrome_elf_unittests.exe, a few tests will fail due
to missing dependencies. Tell the user to build chrome_elf_unittests
instead if they encounter these failures.

BUG=

Review URL: https://codereview.chromium.org/145053002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246975 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246975