Fix bzip2 location
The original URL deleted the older version, but the official home page in https://sourceware.org/bzip2/downloads.html lists https://sourceware.org/pub/bzip2/ as the canonical location.
Closes #4520 (closed)
The original URL deleted the older version, but the official home page in https://sourceware.org/bzip2/downloads.html lists https://sourceware.org/pub/bzip2/ as the canonical location.
Closes #4520 (closed)