Summary:
When initdb fails there is logic to grab the value of the environment variable TEST_TMPDIR. This is not set in all environmnents, and this logic unconditionally dereferences the `char *` `getenv` returns, check-failing.
Jira: DB-17130

Original commit: c05aca31fd610df6dcc9aa871dbb99a67ca588bc / D44696

Test Plan: n/a

Reviewers: bkolagani, amitanand, yyan

Reviewed By: amitanand

Subscribers: slingam, ybase, rthallam, yql

Differential Revision: https://phorge.dev.yugabyte.com/D44732