`#curl_http_content_headers_and_checksum` contains code that works
with a `Content-Type` header in a response but it expects there to
always be only one header in the response. This is normally a
reasonable assumption but we've come across a server that is giving
a response with multiple `Content-Type` headers in the response, so
this produces an error and causes `brew audit` to fail when checking
the URL.
This works around the issue by naively using the last `Content-Type`
header in the response when there's more than one. It's not something
that should normally occur but this will handle the situation when it
does.
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