Skip failing for undefined variables in MacOS (#15744)
Skip failing for undefined variables in MacOS (#15744)

Failing with undefined variables is a good technique to avoid
typos in Bash, but for MacOS this is problematic as bash
used by default on MacOS fails with undefined variable
when there is an empty array passed - which is often needed,
for example when you pass "${@}" arguments.

This PR disables undefined variable check for MacOS.
Acehaidrey/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,mistercrunch/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,bolkedebruin/airflow,apache/airflow,lyft/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,sekikn/incubator-airflow,mistercrunch/airflow,dhuang/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,apache/airflow,Acehaidrey/incubator-airflow,sekikn/incubator-airflow,apache/airflow,dhuang/incubator-airflow,dhuang/incubator-airflow,apache/incubator-airflow,sekikn/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,apache/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,mistercrunch/airflow,nathanielvarona/airflow,bolkedebruin/airflow,lyft/incubator-airflow,sekikn/incubator-airflow,apache/incubator-airflow,danielvdende/incubator-airflow,apache/incubator-airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow