Let clang ci build with 2 threads

14 jobs for clang_parallel
Status Name Job ID Coverage
  Test
passed clang-c++11-Qt4 #2264
Linux

00:18:02

passed clang-c++11-Qt5 #2268
Linux

00:23:26

passed clang-c++98-Qt4 #2272
Linux

00:15:02

passed clang-c++98-Qt5 #2294
Linux

00:18:25

passed gcc-c++11-Qt4 #2263
Linux

00:03:25

passed gcc-c++11-Qt5 #2267
Linux

00:05:02

passed gcc-c++98-Qt4 #2265
Linux

00:02:53

passed gcc-c++98-Qt5 #2271
Linux

00:02:37

failed clang-c++98-Qt4 #2266
Linux

00:00:02

failed clang-c++98-Qt5 #2283
Linux

00:08:37

failed clang-c++98-Qt5 #2274
Linux

00:00:00

failed clang-c++98-Qt5 #2273
Linux

00:00:00

failed clang-c++98-Qt5 #2270
Linux

00:00:02

failed gcc-c++98-Qt5 #2269
Linux

00:00:01