Values:
INTERPRETER_UNSPECIFIED (0):
Invalid for a Windows ExecStepConfig. For a
Linux ExecStepConfig, the interpreter will be
parsed from the shebang line of the script if
unspecified.
SHELL (1):
Indicates that the script is run with /bin/sh on Linux
and cmd on Windows.
POWERSHELL (2):
Indicates that the file is run with PowerShell flags
-NonInteractive, -NoProfile, and
-ExecutionPolicy Bypass.