Turn off old_parser parallelism

I thought it would have been a problem with the -n optimization flag which we
would want to hunt down, but I think it might just be an issue with the parser.
Don't have a good idea why though.

CMakeLists.txt

@@ -209,7 +209,7 @@ add_test(NAME pyston_defaults COMMAND ${PYTHON_EXE} ${CMAKE_SOURCE_DIR}/tools/te
 add_test(NAME pyston_defaults_cpython_tests COMMAND ${PYTHON_EXE} ${CMAKE_SOURCE_DIR}/tools/tester.py -R ./pyston -j${TEST_THREADS} -a=-S -a=-I -k --exit-code-only --skip-failing ${CMAKE_SOURCE_DIR}/test/cpython)
 add_test(NAME pyston_defaults_integration_tests COMMAND ${PYTHON_EXE} ${CMAKE_SOURCE_DIR}/tools/tester.py -R ./pyston -j${TEST_THREADS} -a=-S -k --exit-code-only --skip-failing -t60 ${CMAKE_SOURCE_DIR}/test/integration)
 add_test(NAME pyston_max_compilation_tier COMMAND ${PYTHON_EXE} ${CMAKE_SOURCE_DIR}/tools/tester.py -R ./pyston -j${TEST_THREADS} -a=-O -a=-S -k ${CMAKE_SOURCE_DIR}/test/tests)
-add_test(NAME pyston_old_parser COMMAND ${PYTHON_EXE} ${CMAKE_SOURCE_DIR}/tools/tester.py -a=-x -R ./pyston -j${TEST_THREADS} -a=-n -a=-S -k ${CMAKE_SOURCE_DIR}/test/tests)
+add_test(NAME pyston_old_parser COMMAND ${PYTHON_EXE} ${CMAKE_SOURCE_DIR}/tools/tester.py -a=-x -R ./pyston -j1 -a=-n -a=-S -k ${CMAKE_SOURCE_DIR}/test/tests)
 
 # format
 file(GLOB_RECURSE FORMAT_FILES ${CMAKE_SOURCE_DIR}/src/*.h ${CMAKE_SOURCE_DIR}/src/*.cpp)