Build chapel-py-venv in Arkouda testing (chapel-lang#25795)

Arkouda requires chapel-py to build servers with a non-default
configuration. Eventually we'd like to make it a requirement for any
Arkouda build.

To move in that direction, all of our nightly testing configurations
should be able to build Arkouda using chapel-py (some configurations are
currently resorting to a fallback build mode). This PR update's
Arkouda's sub_test script to `make chapel-py-venv` before attempting to
build Arkouda.

[ reviewed by @bmcdonald3 ] - Thanks!

test/studies/arkouda/sub_test

@@ -54,6 +54,7 @@ fi
 # install frontend python bindings
 (cd $CHPL_HOME && make frontend-shared)
 (cd $CHPL_HOME/tools/chapel-py && python -m pip install .)
+(cd $CHPL_HOME && make chapel-py-venv)
 
 # Compile Arkouda
 if [ "${CHPL_TEST_ARKOUDA_PERF}" = "true" ] ; then