Fix: thread sanitizer result not picked up correctly in CI.

3 jobs from master in 2 minutes 45 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #2647
build_cmake

00:50

 
  Test
passed #2648
run_tests

00:52

 
  Sanitizer
failed #2649
run_thread_sanitizer

01:01

 
[ 80%] Building CXX object test/CMakeFiles/tests.dir/example_tests.cpp.o
[ 90%] Building CXX object test/CMakeFiles/tests.dir/thread_tests.cpp.o
[100%] Linking CXX executable ../bin/tests
[100%] Built target tests
===============================================================================
All tests passed (5 assertions in 4 test cases)

./ci_scripts/run_thread_sanitizer.sh: line 16: exit: ?$: numeric argument required
ERROR: Job failed: exit code 1