Minor fix to chapel-py's run-in-venv script (#26055)

Follow on to: #26050 that adds
some missing double braces to `chapel-py`'s run-in-venv script (forgot
to add this last commit before merging).

[ reviewed by @jabraham17 ] - thanks!

util/config/run-in-venv-with-python-bindings.bash

@@ -26,7 +26,7 @@ if [ $("$python" "$CHPL_HOME/util/chplenv/chpl_sanitizers.py") == "address" ]; t
     exit 1
   fi
 
-  if [ "$CC" == *"clang"* ]; then
+  if [[ "$CC" == *"clang"* ]]; then
     export LD_PRELOAD=$($CC -print-file-name=libclang_rt.asan.so)
   else
     export LD_PRELOAD=$($CC -print-file-name=libasan.so)