ARROW-2745: [C++] ORC ExternalProject needs to declare dependency on vendored protobuf

[xhochy]

We need these dependencies as we otherwise get race conditions in the build.

cc @msarahan @kszucs

[codecov-io]

Codecov Report

Merging #2169 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2169      +/-   ##
==========================================
- Coverage   86.41%   86.39%   -0.02%     
==========================================
  Files         242      230      -12     
  Lines       41622    40730     -892     
==========================================
- Hits        35966    35188     -778     
+ Misses       5656     5542     -114

Impacted Files	Coverage Δ
rust/src/bitmap.rs
rust/src/datatypes.rs
rust/src/record_batch.rs
rust/src/memory.rs
rust/src/lib.rs
rust/src/error.rs
rust/src/buffer.rs
rust/src/list_builder.rs
rust/src/list.rs
rust/src/memory_pool.rs
... and 2 more

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[kszucs]

lz4_static added twice

[xhochy]

good catch, fixed.

[msarahan]

ah, sorry for the oversimplification. I only tested the completely vendored and completely external use cases.

[wesm]

+1, thanks @xhochy!

[xhochy]

Sames Plasma failure as in other PRs.