Powershell doesn't catch CRC errors when unzipping a file (fetcher)

On Windows, Powershell is used to decompress zip files within the fetcher.

In fetcher_tests.cpp, test FetcherTest.Unzip_ExtractInvalidFile, specifically tests for a .zip file with a bad CRC.

On Linux, this is properly decoded, but considered an error since the 'unzip' utility returns 2.

On Windows, this is properly decoded and a success code is returned.

When we move to programmatically decoding container files (tar, gzip, zip, etc), then this issue should be resolved. The test is marked with TODO(jeffaco) for these changes.