Github user majetideepak commented on the issue:
https://github.com/apache/orc/pull/170
In this PR, `FindProtobuf.cmake` checks if the specified path
`PROTOBUF_HOME` contains the required headers and sets `PROTOBUF_INCLUDE_DIRS`,
checks for the library and sets `PROTOBUF_LIBRARIES`, and checks for the
executable and sets `PROTOBUF_EXECUTABLE`. Even if one of them is missing from
the user specified location, the protobuf library gets downloaded. In a future
patch, we can extend the `FindX.cmake` to check default system paths (except
for protobuf). But by default, we should only download.
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