PARQUET-937: Support CMake < 3.4 again for Arrow detection
PARQUET-937: Support CMake < 3.4 again for Arrow detection

pkg_get_variable was introduced in CMake 3.4.
See also: https://cmake.org/cmake/help/latest/release/3.4.html

Author: Kouhei Sutou <kou@clear-code.com>

Closes #283 from kou/support-cmake-3.3-or-older and squashes the following commits:

66462f0 [Kouhei Sutou] Support CMake < 3.4 again for Arrow detection

itaiin/parquet-cpp,apache/parquet-cpp,apache/parquet-cpp,wesm/parquet-cpp,wesm/parquet-cpp,majetideepak/parquet-cpp,MaxRis/parquet-cpp,itaiin/parquet-cpp,majetideepak/parquet-cpp,apache/parquet-cpp,apache/parquet-cpp,itaiin/parquet-cpp,advancedxy/parquet-cpp,advancedxy/parquet-cpp,wesm/parquet-cpp,wesm/parquet-cpp,MaxRis/parquet-cpp,apache/parquet-cpp,majetideepak/parquet-cpp,apache/parquet-cpp,MaxRis/parquet-cpp,majetideepak/parquet-cpp,wesm/parquet-cpp,wesm/parquet-cpp,majetideepak/parquet-cpp,itaiin/parquet-cpp,advancedxy/parquet-cpp,itaiin/parquet-cpp,MaxRis/parquet-cpp,majetideepak/parquet-cpp,MaxRis/parquet-cpp,MaxRis/parquet-cpp,advancedxy/parquet-cpp,advancedxy/parquet-cpp,advancedxy/parquet-cpp,itaiin/parquet-cpp