main/dtc: add py3-libfdt subpackage

pylibfdt is included in the dtc sources and allows using libfdt
from Python.

For some reason, the pylibfdt Makefile ignores $(DESTDIR) at the
moment. Add a small patch to fix this so the Python library is
installed properly. This is just temporary, the next release will
introduce Meson build scripts which do not seem to have that problem.
7 jobs for !16510 with pylibfdt in 24 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
failed #294576
docker-alpine x86_64 allowed to fail
lint

00:00:10

 
  Build
failed #294581
docker-alpine ci-build aarch64
build-aarch64

00:00:06

failed #294582
docker-alpine ci-build armv7
build-armv7

00:00:10

failed #294580
docker-alpine ci-build ppc64le
build-ppc64le

00:00:14

failed #294579
docker-alpine ci-build s390x
build-s390x

00:00:09

failed #294578
docker-alpine ci-build x86
build-x86

00:00:05

failed #294577
docker-alpine ci-build x86_64
build-x86_64

00:00:07

 
Name Stage Failure
failed
build-armv7 Build
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build-x86 Build
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build-x86_64 Build
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lint Lint
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build-s390x Build
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build-ppc64le Build
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build-aarch64 Build
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