* gperftools@2.7: new version
* gperftools: update homepage & url
The URL in the homepage field of the gperftools package redirects to
its GitHub repo, and the URL for version 2.3 returns a 404 error. This
commit updates both fields to the most recent sensible values.
* gperftools: update commit hashes to sha256
This commit deletes the url field for all listed versions because it
is no longer needed as a result of updating the package url field. In
addition, all commit hashes are updated to SHA256.
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