Kernel:stable has an optimized build setup where the kernel-binaries flavor
(kernel-default, debug and so on) are only build-enabled for the
"standard"/"ports" repositories, not for the "QA repositories. 

This makes sense to me and is sensible to optimize rebuild performance on the
build service. however, when I do branch kernel-source, a full project is
replicated under my OBS home project, and that one has build flags enabled for
all the repositories. 

So with other words the branch projects have a lot more packages to build than
the main project. This is because build disables are not inheriting over
branches, they get reset. 

After a chat with the OBS folks, these two options are there:

* set a OBS:BranchSkipRepositories attribute on the project. that means that
new project branches will entirely have the given repositories skipped when
creating a branch. I personally think that isn't the desired behavior, as it
would means things like kernel-obs-build etc are not properly tested

* add a BuildFlags: excludebuild:$packagename to the prjconf. this inherits to
all derived projects, also existing ones, and makes the  disabled-flags setting
obsolete. 

I have tested the following configuration successfully. There might be a script
somewhere that needs to be adapted to generate this project config. otherwise I
think manually maintaining it for now is fine also. 



%if "%_repository" == "QA" || "%_repository" == "QA_ports"  || "%_repository"
== "QA_ARM" || "%_repository" == "QA_PPC" || "%_repository" == "QA_RISCV" ||
"%_repository" == "QA_S390"
BuildFlags: excludebuild:dtb-aarch64
BuildFlags: excludebuild:dtb-armv6l
BuildFlags: excludebuild:dtb-armv7l
BuildFlags: excludebuild:dtb-riscv64
BuildFlags: excludebuild:kernel-64kb
BuildFlags: excludebuild:kernel-debug
BuildFlags: excludebuild:kernel-default
BuildFlags: excludebuild:kernel-docs
BuildFlags: excludebuild:kernel-firmware
BuildFlags: excludebuild:kernel-firmware:compressed
BuildFlags: excludebuild:kernel-kvmsmall
BuildFlags: excludebuild:kernel-lpae
BuildFlags: excludebuild:kernel-pae
BuildFlags: excludebuild:kernel-source
BuildFlags: excludebuild:kernel-syms
BuildFlags: excludebuild:kernel-syzkaller
BuildFlags: excludebuild:kernel-vanilla
BuildFlags: excludebuild:kernel-zfcpdump
BuildFlags: excludebuild:pesign-obs-integration
BuildFlags: excludebuild:qlogic-rules
BuildFlags: excludebuild:systemtap
%endif

%if "%_repository" == "standard" || "%_repository" == "ports"  ||
"%_repository" == "PPC" || "%_repository" == "RISCV" || "%_repository" ==
"S390"
BuildFlags: excludebuild:kernel-obs-build
BuildFlags: excludebuild:kernel-obs-qa
%endif