ARROW-5751: [Python][Packaging] Ensure that c-ares is linked statically in Python wheels

[wesm]

Using the Homebrew provided c-ares results in a shared library dependency. I think it's easier to statically link this than to bundle it

$ otool -L /Users/wesm/miniconda/envs/wheel-test-3.7/lib/python3.7/site-packages/pyarrow/libarrow_flight.14.dylib 
/Users/wesm/miniconda/envs/wheel-test-3.7/lib/python3.7/site-packages/pyarrow/libarrow_flight.14.dylib:
	@rpath/libarrow_flight.14.dylib (compatibility version 14.0.0, current version 14.0.0)
	@rpath/libarrow.14.dylib (compatibility version 14.0.0, current version 14.0.0)
	/usr/local/opt/c-ares/lib/libcares.2.dylib (compatibility version 6.0.0, current version 6.0.0)
	/usr/local/opt/openssl/lib/libssl.1.0.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 307.5.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1238.50.2)

[wesm]

cc @pcmoritz. Is it reasonable to assume that macOS users will have OpenSSL on their systems?

[wesm]

Here's a Crossbow build:

https://travis-ci.org/wesm/crossbow/builds/551375423

I'll have a look later to see if it passed

[wesm]

OK, the patch was successful. Merging

$ otool -L /Users/wesm/miniconda/envs/wheel-test-3.7/lib/python3.7/site-packages/pyarrow/libarrow_flight.14.dylib
/Users/wesm/miniconda/envs/wheel-test-3.7/lib/python3.7/site-packages/pyarrow/libarrow_flight.14.dylib:
	@rpath/libarrow_flight.14.dylib (compatibility version 14.0.0, current version 14.0.0)
	@rpath/libarrow.14.dylib (compatibility version 14.0.0, current version 14.0.0)
	/usr/local/opt/openssl/lib/libssl.1.0.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 307.5.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1238.50.2)