ARROW-6782: [C++] Do not require Boost for minimal C++ build

[wesm]

With these changes, the minimal build now only requires double-conversion_ep. We still have to disable a number of components manually to obtain the minimal build, so there is more work to do

[github-actions]

https://issues.apache.org/jira/browse/ARROW-6782

[nealrichardson]

I'm a little worried about how we're going to maintain this if statement. Suppose the compute module needs boost for something. How are we going to be sure that OR ARROW_COMPUTE gets added here? We won't catch it in our C++ tests because ARROW_BUILD_TESTS will cause boost to be included, and we won't catch it in R or Python because ARROW_PARQUET is on. But then if someone builds with ARROW_COMPUTE but not these other flags, it will fail.

I don't have a solution in mind, just wanted to express my fear.

[wesm]

Yes, I would like to have a more declarative way to define dependencies between components and their build toolchain dependencies rather than doing this ad hoc stuff. The only way to really be sure is to test a battery of different build configurations and make sure they all work

[nealrichardson]

Do all of these require the same boost libraries? Gandiva requires boost::filesystem?

[wesm]

This flag just determines whether or not we create boost_ep (or use the system / toolchain Boost if it's available), so it's an all-or-nothing thing

[wesm]

Appveyor build in progress... https://ci.appveyor.com/project/wesm/arrow/builds/27991887

[wesm]

Weird Appveyor failure that doesn't seem related to this patch

/MANIFESTFILE:release\arrow-public-api-test.exe.manifest" failed (exit code 1120) with the following output:
public_api_test.cc.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: static void __cdecl testing::Test::SetUpTestSuite(void)" (__imp_?SetUpTestSuite@Test@testing@@SAXXZ) referenced in function "public: static void (__cdecl*__cdecl testing::internal::SuiteApiResolver<class testing::Test>::GetSetUpCaseOrSuite(char const *,int))(void)" (?GetSetUpCaseOrSuite@?$SuiteApiResolver@VTest@testing@@@internal@testing@@SAP6AXXZPEBDH@Z)
public_api_test.cc.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: static void __cdecl testing::Test::TearDownTestSuite(void)" (__imp_?TearDownTestSuite@Test@testing@@SAXXZ) referenced in function "public: static void (__cdecl*__cdecl testing::internal::SuiteApiResolver<class testing::Test>::GetTearDownCaseOrSuite(char const *,int))(void)" (?GetTearDownCaseOrSuite@?$SuiteApiResolver@VTest@testing@@@internal@testing@@SAP6AXXZPEBDH@Z)
release\arrow-public-api-test.exe : fatal error LNK1120: 2 unresolved externals
[192/516] Building CXX object src\arrow\CMakeFiles\arrow-array-test.dir\array_binary_test.cc.obj
ninja: build stopped: subcommand failed.

[wesm]

The CI is passing here, the Appveyor failure is ARROW-6834

[pitrou]

+1