compilation-environment

compilation-environment is a variable defined in `compile.el'.
Its value is

nil

Documentation:
List of environment variables for compilation to inherit.
Each element should be a string of the form ENVVARNAME=VALUE.
This list is temporarily prepended to `process-environment' prior to
starting the compilation process.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.