SDK container: include circular deps pkgs (#2340)

This change builds all packages required to break circular dependencies
and includes these in the SDK image. This way, emerge-<arch> can be used
right away and build_packages only builds packages with production USE
flags.

The change significantly reduces the build time at the cost of a larger
SDK image and longer SDK container build time. Uncompressed:
               Size before       Size after
all arches       7.75GB             9.29GB
arm64            5.7GB              6.58GB
amd64            5.64GB             6.45GB

Signed-off-by: Thilo Fromm <thilofromm@microsoft.com>

sdk_lib/Dockerfile.sdk-build

@@ -9,9 +9,11 @@ RUN echo "export COREOS_OFFICIAL=$OFFICIAL" > /mnt/host/source/.env
 
 RUN /home/sdk/sdk_entry.sh ./setup_board --board="arm64-usr" --binhost="${BINHOST}/arm64-usr"
 RUN /home/sdk/sdk_entry.sh ./setup_board --board="arm64-usr" --regen_configs
+RUN /home/sdk/sdk_entry.sh ./build_packages --board="arm64-usr" --only_resolve_circular_deps
 
 RUN /home/sdk/sdk_entry.sh ./setup_board --board="amd64-usr" --binhost="${BINHOST}/amd64-usr"
 RUN /home/sdk/sdk_entry.sh ./setup_board --board="amd64-usr" --regen_configs
+RUN /home/sdk/sdk_entry.sh ./build_packages --board="amd64-usr" --only_resolve_circular_deps
 
 RUN rm /mnt/host/source/.env
 RUN rm -rf /home/sdk/toolchain-pkgs