Adding new tests using runDaphne can cause test.sh to run indefinitely

[AlexRTer]

When adding new test cases in #922, I noticed the test.sh script ran indefinitely. One of the tests it gets stuck on (ewBinarySub) runs test/api/cli/codegen/ewbinary_sub.daphne which runs correctly if executed on its own (with and without codegen).
EwBinaryTest's testing function calls runDaphne -> runProgram and seems to get stuck on the first dup2 call at line 117 which never returns/finishes.
This could be related to the issue of leaking file descriptors that was fixed in c2900a3. The mentioned PR is the smallest addition I am currently aware of to trigger this issue.