On the testing machines, we can still see QTCREATORBUG-18607 in tst_CSUP03 although it is said to fixed. I can reproduce this on my machine when libclang.dll is neither in PATH nor in Creator's bin directory. If I put the dll there, the test does not fail anymore.

While Creator complains about the missing dll when started directory, everything seems to work well when it is being started from Squish. I assume that Squish uses some internal version of libclang which runs into this error.

Could you please check whether libclang.dll 3.9 is in Creator's bin directory for the Squish runs? If not, let's try if copying it there will fix the fails.