tools/ci.sh: Increase timeout for stackless clang test runs.

Stackless mode makes `tests/thread/stress_aes.py` slow, around 75 seconds
for this CI job (probably due to contention among the many threads for the
GC lock, to allocate frames for function calls).  So increase the timeout
to allow this test to pass.

Signed-off-by: Damien George <damien@micropython.org>

tools/ci.sh

@@ -720,7 +720,8 @@ function ci_unix_stackless_clang_build {
 }
 
 function ci_unix_stackless_clang_run_tests {
-    ci_unix_run_tests_helper CC=clang
+    # Timeout needs to be increased for thread/stress_aes.py test.
+    MICROPY_TEST_TIMEOUT=90 ci_unix_run_tests_helper CC=clang
 }
 
 function ci_unix_float_clang_build {