Fix for device_utils Install when BUILDTYPE env var not set.
Fix for device_utils Install when BUILDTYPE env var not set.

If you have not built the md5bin and have not set the BUILDTYPE
env variable the Install function will crash. I would like to use
this install function to install apks downloaded from google
storage (where the user may have never built any of Chromium).

BUG=

Review URL: https://codereview.chromium.org/1368843002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#350739}

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