Pull default build type from environment variable

Change-Id: I42eadd763a4211f72e1f12257b6d0a174f6b9684

python/setup.py

@@ -103,7 +103,7 @@ class build_ext(_build_ext):
     def initialize_options(self):
         _build_ext.initialize_options(self)
         self.extra_cmake_args = os.environ.get('PYARROW_CMAKE_OPTIONS', '')
-        self.build_type = 'debug'
+        self.build_type = os.environ.get('PYARROW_BUILD_TYPE', 'debug')
 
     CYTHON_MODULE_NAMES = [
         'array',