DefaultEnvironment returns default environment.

EnvironmentDownloadBaseURL is the base url to download environment image.

EnvironmentImageFileExtension is extension for environment image file.

EnvironmentRootPassword is password for admin account.

EnvironmentUsername is username for regular account.

EnvironmentUserPassword is password for regular account.

CrossBuildHomeDirPath is the crossbuild home directory.

EnvironmentImageDirPath is the directory that keeps environment images.

ErrMsgEnvironmentInitFailed occurs if environment initialization failed.

SupportedEnvironmentsFileName is name of the file that list supported environments.

Environment is a virtualized crossbuild operating system.

EnvironmentCommand is one or more command lines to be executed.