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ARROW-9004: [C++][Gandiva] Support building with LLVM 10

LLVM 7 and 8 are still supported.

Clang Tools still use 8 because Clang Tools 10 reports an error for
RaipdJSON in sanitizer build. We should work on this as a separated
task.

e.g.:

https://github.com/kou/arrow/runs/725786805?check_suite_focus=true

    /usr/include/rapidjson/internal/stack.h:117:13: runtime error: applying non-zero offset 16 to null pointer
         #0 0x7f4d336c0e2c in void arrow::rapidjson::internal::Stack<arrow::rapidjson::CrtAllocator>::Reserve<arrow::rapidjson::GenericValue<arrow::rapidjson::UTF8<char>, arrow::rapidjson::MemoryPoolAllocator<arrow::rapidjson::CrtAllocator> > >(unsigned long) /usr/include/rapidjson/internal/stack.h:117:13

Ubuntu 16.04 still use LLVM 8 because LLVM 10 requires C++ 14 but g++
5 on Ubuntu 16.04 is too old to use
cpp/src/arrow/vendored/datetime/date.h.

CentOS 8 packages still use LLVM 8 because there are no packages for
LLVM 10 on CentOS 8.

manylinux1 still use LLVM 8 because g++ 4.8.2 is old to build LLVM 9
or later.

Conda package for Windows still use LLVM 8 because llvmdev 9 or later
use Visual Studio 2017. We need to use Visual Studio 2017 not 2015 to
use llvmdev 9 or later.

Closes #7323 from kou/cpp-llvm-10

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>