build-webos: Add WEBOS_DISTRO_BUILD_ID to BB_ENV_EXTRAWHITE

Adding WEBOS_DISTRO_BUILD_ID to BB_ENV_EXTRAWHITE makes it possible to
override it with environment variable

[GF-2461] Invent build variable with build number and Jenkins job name

Open-webOS-DCO-1.0-Signed-off-by: Janne Hurskainen <janne.hurskainen@palm.com>