Replace the temp dir in dart_analyze.py's output with the package name.
Replace the temp dir in dart_analyze.py's output with the package name.

This prints "wget_package.dartzip:main.dart" intstead of
"/tmp/<garbage>/main.dart".

BUG=459376
R=hansmuller@google.com

Review URL: https://codereview.chromium.org/996703003

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