builddeb: make headers package thinner
Remove a bunch of files not used during external module builds:
- foreign architecture headers
- subtree Makefiles
- Kconfig files
- perl scripts
On amd64 system this looses a third of the resulting .deb size.
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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