PARQUET-940: Fix a bug that Arrow libraries may not be found
PARQUET-940: Fix a bug that Arrow libraries may not be found

If we find Arrow by pkg-config and Arrow is installed into system
directory such as /usr, Arrow libraries can't be found. Because
pkg-config omits system directory from ARROW_LIBRARY_DIRS. In this case,
ARROW_LIBS is empty then Arrow libraries aren't found.

We should use ARROW_LIB_DIR (= $(pkg-config arrow --variable=libdir)
instead of ARROW_LIBRARY_DIRS. It always returns directory that has
Arrow libraries.

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

Closes #286 from kou/fix-arrow-lib-dir-detection and squashes the following commits:

2d54baf [Kouhei Sutou] Fix a bug that Arrow libraries may not be found

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