* Introduce build variable HAIKU_IMAGE_ADDITIONAL_PACKAGES which can be
set to add additional packages to the image.
* Use HAIKU_IMAGE_ADDITIONAL_PACKAGES to support specifying a list of
additional packages via the build-package-list build profile action.
* Add htmldoc and texi2html when building the list of the packages for
which we need source packages when building the bootstrap Haiku image.
We don't want them on the regular image, but they are needed to build
some packages that are on it.
24796718b9