ci(macos): Use venv instead of global install

brew/python doesn't like installing python packages globally:
```
error: externally-managed-environment
× This environment is externally managed
```

Author: yedayak

test/macos-script.sh

@@ -8,12 +8,15 @@ brew install \
     automake \
     bash
 
-python3 -m pip install -r test/requirements.txt
-
 oldpwd=$(pwd)
 cp -a . /work
 cd /work
 
+python3 -m venv venv
+#shellcheck disable=SC1091
+source venv/bin/activate
+python3 -m pip install -r test/requirements.txt
+
 export bashcomp_bash=bash
 env