Setting output_dir for extract_ir_test (#238)

Otherwise the test won't run from the command line.

Author: mtrofin

compiler_opt/tools/extract_ir_test.py

@@ -23,6 +23,7 @@
 from compiler_opt.tools import extract_ir
 
 flags.FLAGS['num_workers'].allow_override = True
+flags.FLAGS['output_dir'].value = ''
 
 
 class ExtractIrTest(absltest.TestCase):