PARQUET-959: Set CMAKE_INSTALL_LIBDIR in Arrow thirdparty build to avoid failures on multiarch systems

Arrow libraries are now installed in `lib64` on multiarch systems, which breaks the thirdparty build

Author: Wes McKinney <wes.mckinney@twosigma.com>

Closes #303 from wesm/PARQUET-959 and squashes the following commits:

168afa3 [Wes McKinney] Set CMAKE_INSTALL_LIBDIR in Arrow thirdparty build to avoid failures on systems with multiarch
diff --git a/cmake_modules/ThirdpartyToolchain.cmake b/cmake_modules/ThirdpartyToolchain.cmake
index 2b31e97..967c3c4 100644
--- a/cmake_modules/ThirdpartyToolchain.cmake
+++ b/cmake_modules/ThirdpartyToolchain.cmake
@@ -365,12 +365,14 @@
   set(ARROW_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/arrow_ep/src/arrow_ep-install")
   set(ARROW_HOME "${ARROW_PREFIX}")
   set(ARROW_INCLUDE_DIR "${ARROW_PREFIX}/include")
-  set(ARROW_SHARED_LIB "${ARROW_PREFIX}/lib/libarrow${CMAKE_SHARED_LIBRARY_SUFFIX}")
-  set(ARROW_STATIC_LIB "${ARROW_PREFIX}/lib/libarrow.a")
+  set(ARROW_LIB_DIR "${ARROW_PREFIX}/lib")
+  set(ARROW_SHARED_LIB "${ARROW_LIB_DIR}/libarrow${CMAKE_SHARED_LIBRARY_SUFFIX}")
+  set(ARROW_STATIC_LIB "${ARROW_LIB_DIR}/libarrow.a")
   set(ARROW_CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
     -DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}
     -DCMAKE_C_FLAGS=${CMAKE_C_FLAGS}
     -DCMAKE_INSTALL_PREFIX=${ARROW_PREFIX}
+    -DCMAKE_INSTALL_LIBDIR=${ARROW_LIB_DIR}
     -DARROW_JEMALLOC=OFF
     -DARROW_IPC=OFF
     -DARROW_BUILD_TESTS=OFF)