With this its possible to create custom environment variables within the kas
configuration file, that are passed through to the build environment:
env:
VARIABLE_NAME: "default variable value"
Those variables can be overwritten by variables of the environment kas is
started in:
$ VARIABLE_NAME="overwritten variable value" kas shell ...
Those variables are also added to the 'BB_ENV_EXTRAWHITE' variable list to make
them available to bitbake.
This is useful for instance storing sensitive information, that should not be
part of the configuration files or bitbake recipes.
Signed-off-by: Claudius Heine <ch@denx.de>